Photocatalyst-coated body and photocatalytic coating liquid therefor

ABSTRACT

A photocatalyst-coated body comprises a substrate and a photocatalyst layer provided on the substrate, the photocatalyst layer comprising photocatalyst particles of 1 part or more by mass and less than 20 parts by mass, inorganic oxide particles of 70 parts or more by mass and less than 99 parts by mass, and the dried substance of a hydrolyzable silicone of zero parts or more by mass and less than 10 parts by mass, provided that a total amount of the photocatalyst particles, the dried substance of the inorganic oxide particles and the hydrolyzable silicone is 100 parts by mass in terms of silica, wherein the photocatalyst layer has a film thickness of 3.0 μm or less.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/383,840 filed on Mar. 27, 2009, which is a continuation-in-part ofU.S. patent application Ser. No. 12/079,417 filed on Mar. 26, 2008. TheU.S. patent application Ser. No. 12/383,840 claims the benefit of U.S.Provisional Application No. 61/040,151 filed Mar. 28, 2008, and claimspriorities to Japanese Patent Application No. 2008-87837 filed Mar. 28,2008, Japanese Patent Application No. 2008-87840 filed Mar. 28, 2008,Japanese Patent Application No. 2008-244432 filed Sep. 24, 2008, andJapanese Patent Application No. 2008-331910 filed Dec. 26, 2008. Theentire disclosures of these applications are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a photocatalyst-coated body which issuperior in weather resistance, noxious gas decomposability, and variouscoating properties, particularly suitable for use in exterior materialsfor buildings and the like. The present invention also relates to aphotocatalyst coating liquid for the photocatalyst-coated body.

BACKGROUND ART

Photocatalysts such as titanium oxide have been recently utilized invarious applications such as exterior materials for buildings.Employment of the photocatalyst makes it possible to harness lightenergy to decompose various types of noxious substances and tohydrophilize the surface of a substrate coated with the photocatalyst toallow a stain deposited on the surface to be easily washed away withwater. The following techniques have been known for producingphotocatalyst-coated bodies coated with such a photocatalyst.

It is known to use an aqueous dispersion comprising photocatalyticmetallic oxide particles, a colloidal silica, and a surfactant to imparthydrophilic properties to the surface of a synthetic resin or the like(see, for example, Japanese Patent Laid-Open Publication No.1999-140432). In this technique, the hydrophilic properties areintensified by adding a large amount of a surfactant ranging from 10 wt% to 25 wt %. Also, the film thickness is set at 0.4 μm or less in orderto prevent white turbidity from being caused by diffuse reflection oflight.

It is also known to form on the substrate a coating film comprising aphotocatalytic titanium dioxide and a binder silica sol to obtain aphotocatalyst body (see, for example, Japanese Patent Laid-Open No.1999-169727). In this technique, the additive amount of the silica solin view of SiO₂ is 20 parts to 200 parts by weight of the titaniumdioxide, and the TiO₂ content ratio is high. The particle diameter ofthe silica sol is as small as 0.1 nm to 10 nm.

It is also known that a photocatalyst coating material is used to form aphotocatalyst coating film that transmits 50% or more of light having awavelength of 500 nm and blocks 80% or more of light having a wavelengthof 320 nm (see, for example, in Japanese Patent Laid-Open No.2004-359902). In this technique, an organosiloxane partial hydrolysateis used as a binder of the photocatalyst coating material, in which theorganosiloxane partial hydrolysate is contained preferably in an amountof 5 mass % to 40 mass % of the entire coating composition.

In the meantime, a problem has been conventionally known that, when asubstrate for a photocatalyst layer is composed of an organic material,the organic material is decomposed or deteriorated due to photocatalyticactivity of the photocatalyst. In order to address this problem, it isknown that an adhesive layer made of a silicone-modified resin or thelike is provided between a photocatalyst layer and a substrate toprotect the substrate from being deteriorated by the photocatalysis(see, for example, WO97/00134).

SUMMARY OF THE INVENTION

The inventors have currently found that a photocatalyst-coated bodywhich is superior in weather resistance, noxious gas decomposability,and various coating properties (such as ultraviolet absorptivity,transparency and film strength) can be obtained while preventingcorrosion of a substrate (in particular an organic substrate), byconstituting a photocatalyst layer with a specified composition thatcomprises photocatalyst particles and inorganic oxide particles in aspecified mass ratio and minimizing a hydrolyzable silicone and asurfactant to no or a small amount.

Accordingly, it is an object of the present invention to provide aphotocatalyst-coated body, which is superior in weather resistance,noxious gas decomposability, and various coating properties (such asultraviolet absorptivity, transparency and film strength) whilepreventing corrosion of a substrate (in particular an organicsubstrate). It is also an object of the present invention to provide aphotocatalyst coating liquid for the photocatalyst-coated body.

According to an aspect of the present invention, there is provided aphotocatalyst-coated body comprising a substrate and a photocatalystlayer provided on the substrate, the photocatalyst layer comprising:photocatalyst particles of 1 part or more by mass and less than 20 partsby mass; inorganic oxide particles of 70 parts or more by mass and lessthan 99 parts by mass; and

a hydrolyzable silicone of zero parts or more by mass and less than 10parts by mass, provided that a total amount of the photocatalystparticles, the inorganic oxide particles and the hydrolyzable siliconeis 100 parts by mass.

According to another aspect of the present invention, there is provideda photocatalyst coating liquid used for manufacturing thephotocatalyst-coated body according to any one of claims 1 to 11,comprising, in a solvent, photocatalyst particles of 1 part or more bymass and less than 20 parts by mass; inorganic oxide particles of 70parts or more by mass and less than 99 parts by mass; and a hydrolyzablesilicone of zero parts or more by mass and less than 10 parts by mass,provided that the total amount of the photocatalyst particles, theinorganic oxide particles and the hydrolyzable silicone is 100 parts bymass.

According to the present invention there is also provided aphotocatalyst-coated body comprising a substrate and a photocatalystlayer provided on the substrate, the photocatalyst layer comprising:photocatalyst particles of 1 part or more by mass and less than 20 partsby mass; inorganic oxide particles of 70 parts or more by mass and lessthan 99 parts by mass; and the dried substance of a hydrolyzablesilicone of zero parts or more by mass and less than 10 parts by mass,provided that a total amount of the photocatalyst particles, the driedsubstance of the inorganic oxide particles and the hydrolyzable siliconeis 100 parts by mass in terms of silica, wherein the photocatalyst layerhas a film thickness of 3.0 μm or less.

Similarly according to the present invention there is provided aphotocatalyst coating liquid used for manufacturing thephotocatalyst-coated body according to claim 1, comprising, in asolvent, photocatalyst particles of 1 part or more by mass and less than20 parts by mass; inorganic oxide particles of 70 parts or more by massand less than 99 parts by mass; and a hydrolyzable silicone of zeroparts or more by mass and less than 10 parts by mass, provided that thetotal amount of the photocatalyst particles, the inorganic oxideparticles and the hydrolyzable silicone is 100 parts by mass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between the values Δb being achange in color difference between before and after the accelerated testand TiO₂ content ratios, measured in Examples 1 to 7, in which thevalues of the TiO₂ content ratios (parts by mass) represent theproportion of the mass of the titanium oxide particles to the totalamount of the titanium oxide particles and the silica particles.

FIG. 2 is a graph showing the relationship between the lineartransmittance at 550 nm (%) and the film thickness (μm), measured inExamples 12 to 19, in which the ratios of 1/99, 5/95, 10/90 representthe titanium-particle/silica-particle mass ratio.

FIG. 3 is a graph showing the relationship between the ultraviolet (300nm) shield rate (%) and the film thickness (μm), measured in Examples 12to 19, in which the ratios of 1/99, 5/95, 10/90 represent thetitanium-particle/silica-particle mass ratio.

DETAILED DESCRIPTION OF THE INVENTION Photocatalyst-Coated Body

The photocatalyst-coated body according to the present inventioncomprises a substrate and a photocatalyst layer provided on thesubstrate. The photocatalyst layer includes 1 part or more and less than20 parts by mass of photocatalyst particles, 70 parts or more and lessthan 99 part by mass of inorganic oxide particles, zero parts or moreand less than 10 parts by mass of a hydrolyzable silicone as an optionalcomponent, and zero parts or more and less than 10 parts by mass of asurfactant as an optional component. The total amount of thephotocatalyst particles, the inorganic oxide particles, and thehydrolyzable silicone is 100 parts by mass, and the parts by mass of thesurfactant are determined with respect to the total 100 parts by mass.

The photocatalyst layer according to the present invention basicallycomprises 1 part or more and less than 20 parts by mass of photocatalystparticles and 70 parts or more and less than 99 parts by mass ofinorganic oxide particles. This constitution makes it possible toachieve a photocatalyst-coated body which is superior in weatherresistance, noxious gas decomposability, and various coating properties(such as ultraviolet absorptivity, transparency and film strength) whilepreventing corrosion of a substrate (in particular an organicsubstrate). The reason why these effects are realized all together isnot clear, but may be supposed to be as follows. The followingexplanation is only a hypothesis, and the present invention is notlimited by the following hypothesis. First, since the photocatalystlayer basically comprises two kinds of particles, i.e., thephotocatalyst particles and the inorganic oxide particles, there is alot of space between the particles. In the case of using a large amountof a hydrolyzable silicone widely used as a binder for a photocatalystlayer, it is considered that the hydrolyzable silicone would blockdiffusion of the gas because the space between particles is closelyfilled up. However, the photocatalyst layer of the present invention isfree from a hydrolyzable silicone or, in the alternative, comprises thehydrolyzable silicone of less than 10 parts by mass with respect to thetotal 100 parts by mass of the photocatalyst particles, the inorganicoxide particles and the hydrolyzable silicone. For this reason, it issupposed that the space between particles can be sufficiently ensured.The space thus ensured leads to realization of a structure in whichnoxious gases such as NOx and SOx are readily diffused into thephotocatalyst layer. As a result, it is supposed that the noxious gasescome into effective contact with the photocatalyst particles to bedecomposed by the photocatalyst activity.

At the same time, it is considered that, since the proportion of thephotocatalyst particles is quite lower than that of the inorganic oxideparticles, direct contact of the photocatalyst particles with thesubstrate can be minimized to suppress corrosion of the substrate (inparticular the organic substrate). It is also supposed that thesubstrate can be prevented from being damaged from ultraviolet lightbecause the photocatalyst itself absorbs ultraviolet light to reduce theamount of ultraviolet light reaching the substrate. As a result, thephotocatalyst layer of the present invention is able to be formed on asubstrate of which at least the surface is composed of an organicmaterial, by direct application without interposing an intermediatelayer for protecting the substrate. Thus, since there is no necessity toform the intermediate layer, it is possible to save time and costrequired for manufacturing photocatalyst-coated bodies. In addition, thephotocatalyst layer of the present invention may not comprise asurfactant, but even if the photocatalyst layer comprises thesurfactant, the amount of surfactant is set to less than 10 parts bymass with respect to the total 100 parts by mass of the photocatalystparticles, the inorganic oxide particles and the hydrolyzable silicone.By this setting, it is supposed to prevent deterioration in filmstrength and noxious gas decomposability, which is caused by a largeamount of the surfactant being contained. With the above variousphenomena occurring all together, it is thought to achieve aphotocatalyst-coated body which is superior in weather resistance,noxious gas decomposability, and various coating properties (such asultraviolet absorptivity, transparency and film strength) whilepreventing corrosion of a substrate (in particular an organicsubstrate).

Additionally the photocatalyst-coated body according to the presentinvention may be a photocatalyst-coated body comprising a substrate anda photocatalytic layer provided on the substrate, the photocatalyticlayer comprising photocatalytic particles and inorganic oxide particles,and the photocatalytic layer having interstices between the particles inthe layer.

By constructing the photocatalytic layer with photocatalytic particlesand inorganic oxide particles as main components and positivelyproviding interstices between the particles in the photocatalytic layer,air permeability to the photocatalytic layer is improved, while itbecomes easier to allow decomposable substances such as NOx gas inoutside air or gases such as oxygen and water vapor necessary togenerate active oxygen to undergo an action effectively in the vicinityof the photocatalytic particles. Accordingly, gas decompositioncharacteristics of the photocatalyst such as excellent NOx decompositionfunction are obtained.

In addition to the aforementioned construction, it is preferable thatthe photocatalyst-coated body is constructed so that the photocatalyticlayer comprises the photocatalytic particles in an amount of more than 1part by mass and less than 5 parts by mass, the inorganic oxideparticles in an amount of more than 85 parts by mass and less than 99parts by mass, and the dried substance of the hydrolyzable silicone inan amount of 0 part by mass or more and less than 10 parts by mass,provided that the photocatalytic particles, the inorganic oxideparticles, and the hydrolyzable silicone amount to 100 parts by mass interms of silica.

That is, it is considered that considerably lower content of thephotocatalytic particles than that of the inorganic oxide particles inthe photocatalytic layer (preferably more than 1 part by mass and lessthan 5 parts by mass, more preferably 2 parts by mass or more and lessthan 5 parts by mass, further more preferably 2 parts by mass or moreand 4.5 part by mass or less relative to the total amount of 100 partsby mass of the photocatalytic particles, inorganic oxide particles andhydrolyzable silicone) enables to minimize the direct contact of thephotocatalytic particles with the substrate, making erosion of thesubstrate (especially the organic substrate) less likely to occur. Inaddition, it is considered that deterioration of the substrate byultraviolet light can be reduced by reducing the dose of the ultravioletlight reaching the substrate since the photocatalyst itself absorbs theultraviolet light.

At the same time, with this construction, it becomes possible to obtaina photocatalyst-coated body excellent in harmful gas decomposability andvarious desired coating characteristics (such as transparency and filmstrength), while preventing erosion of the substrate (especially theorganic substrate). First of all, since the amount of the inorganicoxide particles is as large as preferably more than 85 parts by mass andless than 99 parts by mass, the photocatalytic layer is essentiallycomposed of two types of the particles, photocatalytic particles andinorganic oxide particles, resulting in existence of plentifulinterstices between the particles. If a large amount of hydrolyzablesilicone which is commonly used as a binder of the photocatalytic layeris used, it is considered that the gas diffusion is hindered becausesuch interstices between the particles are densely filled with thehydrolyzable silicone. On the other hand, since the photocatalytic layerof the present invention does not comprise the dried substance of thehydrolyzable silicone or, even if it comprises some, the content ispreferably less than 10 parts by mass relative to the total amount of100 parts by mass of the photocatalytic particles, the inorganic oxideparticles, and the dried substance of the hydrolyzable silicone in termsof silica, interstices between the particles can be sufficientlymaintained and secured, and thus attain a structure which facilitatesdiffusion of the harmful gases such as NOx and SOx into thephotocatalytic layer. As a result, it is considered that the harmfulgases effectively contact with the photocatalytic particles and aredecomposed by the photocatalytic activity. Considering theaforementioned action and effect, it is the most preferable that theamount of the dried substance of the hydrolyzable silicone in terms ofsilica is substantially 0 part by mass.

In the aforementioned construction, especially the photocatalyticparticles can exert photocatalytic decomposition function such as afunction to decompose NOx in an amount as small as preferably more than1 part by mass and less than 5 parts by mass. Therefore, it isconsidered that the photocatalyst-coated body excellent in weatherresistance, hydrophilicity, harmful gas decomposability and variousdesired coating characteristics (such as transparency and film strength)is realized, while preventing erosion of the substrate (especially theorganic substrate). Accordingly, the photocatalytic layer of the presentinvention can exert excellent durability even with high ultraviolet doseand under hot and humid weather conditions in tropical and subtropicalregions especially at low latitudes, at the same time as thephotocatalytic decomposition function.

The average particle diameter of the photocatalytic particles ispreferably 10 nm or more and 100 nm or less, more preferably 10 nm ormore and 60 nm or less. The average particle diameter is calculated as anumber average value of the measured length of arbitrary 100 particleswithin a visual field of a scanning electron microscope with 200,000×magnification. Although the most preferred shape of the particle isperfect sphere, approximate circle or ellipse may be acceptable, inwhich case the length of the particle is approximately calculated as((major axis+minor axis)/2). In this range, gas permeation amount in thephotocatalytic layer, specific surface area for sufficient gasdecomposition activity, monocrystalline size for sufficientphotocatalytic activity of the particle, and various coating filmcharacteristics such as transparency and weather resistance can beexerted in a balanced manner. Furthermore, making the average particlediameter of the photocatalytic particles 10 nm or more and 100 nm orless, more preferably 10 nm or more and 60 nm or less can be suitablycombined with each of the constituent elements of the present inventiondescribed up to here, and new effects mentioned above may also beexerted without hindering the effects of the constituent elements.

As the photocatalytic particles, particles of metal oxide such astitanium oxide (TiO₂), ZnO, SnO₂, SrTiO₃, WO₃, Bi₂O₃, and Fe₂O₃ areexemplified. Any metal oxides exemplified here can be suitably combinedwith each constituent mentioned above.

As the photocatalytic particles, titanium oxide particles arepreferable. Titanium oxide has better water resistance compared with ZnOand exerts photocatalytic function such as gas decomposition by thelight of the wavelength of 380 nm to 420 nm which is includedsufficiently in sunlight compared with SnO₂. Furthermore, microparticlesof a nanometer order of titanium oxide are more easily available thanSrTiO₃, therefore the specific surface area is large and practicallysufficient photocatalytic activity is easily available. Furthermore, dueto its larger bandgap compared with WO₃, Bi₂O₃, and Fe₂O₃, titaniumoxide has a sufficient oxidation power, prevents recoupling ofconductive electron and positive hole after photoexcitation, and hasactivation energy sufficient for gas decomposition. In addition,titanium oxide is harmless, chemically stable, and available at lowcost. In addition, due to its high bandgap energy, titanium oxide needsultraviolet light for photoexcitation and does not absorb visible lightin the process of photoexcitation, resulting in no coloration bycomplementary color component.

Using titanium oxide particles as the photocatalytic particles can besuitably combined with each of the constituent elements of the presentinvention described up to here, and new effects mentioned above may alsobe exerted without hindering the effects of the constituent elements.

As the photocatalytic particles, anatase-type titanium oxide ispreferable among titanium oxide particles. Anatase-type titanium oxidehas an oxidation power stronger than rutile-type titanium oxide andexerts stronger photocatalytic function such as gas decomposition.Furthermore, using anatase-type titanium oxide particles as thephotocatalytic particles can be suitably combined with each of theconstituent elements of the present invention described up to here, andnew effects mentioned above may also be exerted without hindering theeffects of the constituent elements.

It is preferable that Cu component is further present in thephotocatalytic layer. Cu itself has excellent antifungal characteristicsand excellent adsorption characteristics for harmful gases and acts onthe photocatalytic particles to decrease the probability of recouplingof conductive electron and positive hole generated by photoexcitation ofthe photocatalyst, resulting in increasing the oxidation power and gasdecomposition power of the photocatalytic particles. Larger effect isexerted if the photocatalyst is a photocatalyst having intrinsicallystrong oxidation power, such as titanium oxide, especially anatase-typetitanium oxide. Furthermore, making Cu present in the photocatalyticlayer can be suitably combined with each of the constituent elements ofthe present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

It is preferable that Cu component is supported on the photocatalyticparticles. The embodiment in which not only Cu is present in thephotocatalytic layer but also is positively supported on thephotocatalytic particles can further enhance the effect of Cu to act onthe photocatalytic particles to decrease the probability of recouplingof conductive electron and positive hole generated by photoexcitation ofthe photocatalyst, resulting in increasing the oxidation power and gasdecomposition power of the photocatalytic particles. Larger effect isexerted if the photocatalyst is a photocatalyst having intrinsicallystrong oxidation power, such as titanium oxide, especially anatase-typetitanium oxide. Furthermore, making Cu positively supported on thephotocatalytic particles can be suitably combined with each of theconstituent elements of the present invention described up to here, andnew effects mentioned above may also be exerted without hindering theeffects of the constituent elements.

It is preferable that both of the Cu component and the Ag component arepresent in the photocatalytic layer. Presence of both of Cu and Ag inthe photocatalytic layer not only exerts the excellent antifungalcharacteristics of Cu and the excellent antibacterial characteristics ofAg simultaneously, but substantially increases the decompositionactivity of the photocatalyst. Although the mechanism is not clear atpresent, mutual interactions among the photocatalytic particles, Ag, andCu are presumably correlated. Larger effect is exerted if thephotocatalyst is a photocatalyst having intrinsically strong oxidationpower, such as titanium oxide, especially anatase-type titanium oxide.Furthermore, making both of Cu and Ag present in the photocatalyticlayer can be suitably combined with each of the constituent elements ofthe present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

It is preferable that both of the Cu component and the Ag component aresupported on the photocatalytic particles. The embodiment in which notonly Cu and Ag are present in the photocatalytic layer but also both ofCu and Ag are supported on the photocatalytic particles can furtherenhance the effect of Cu and Ag to act on the photocatalytic particlesto decrease the probability of recoupling of conductive electron andpositive hole generated by photoexcitation of the photocatalyst,resulting in increasing the oxidation power and gas decomposition powerof the photocatalytic particles. Larger effect is exerted if thephotocatalyst is a photocatalyst having intrinsically strong oxidationpower, such as titanium oxide, especially anatase-type titanium oxide.Furthermore, making both of Cu and Ag positively supported on thephotocatalytic particles can be further suitably combined with each ofthe constituent elements of the present invention described up to here,and new effects mentioned above may also be exerted without hinderingthe effects of the constituent elements.

As the inorganic oxide particles in the photocatalytic layer, forexample, particles of single oxide such as silica, alumina, zirconia,ceria, yttria, boronia, magnesia, calcia, ferrite, iron oxide, amorphoustitania, hafnia, tin oxide, manganese oxide, niobium oxide, nickeloxide, cobalt oxide, indium oxide, lanthanum oxide, barium oxide, etc.;or complex oxide such as aluminosilicate, barium titanate, calciumsilicate, etc. can be suitably used.

It is considered that mixing the inorganic oxide particles canmoderately decrease the amount of the photocatalyst and minimize thedirect contact of the photocatalytic particles with the substrate to theminimum, while securing the gas permeability in the photocatalyticlayer, thereby making the erosion of the substrate (especially theorganic substrate) less likely to occur. In addition, it is consideredthat deterioration of the substrate by ultraviolet light can be reducedby reducing the dose of the ultraviolet light reaching the substratesince the photocatalyst itself absorbs the ultraviolet light.

Furthermore, using the aforementioned inorganic oxide particles can besuitably combined with each of the constituent elements of the presentinvention described up to here, and new effects mentioned above may alsobe exerted without hindering the effects of the constituent elements.

As the inorganic oxide particles in the photocatalytic layer, silica isthe most preferable. Mixing silica increases the hydrophilicity of thephotocatalytic layer, and the photocatalytic layer being washed by withwater or rainwater effectively prevents the stain adhered to the surfacefrom decreasing the decomposition function of the photocatalyst. Thispreventive effect is especially enhanced if the photocatalyst is aphotocatalyst having intrinsically strong oxidation power, such astitanium oxide, especially anatase-type titanium oxide. Furthermore,using silica particles as the inorganic oxide particles can be suitablycombined with each of the constituent elements of the present inventiondescribed up to here, and new effects mentioned above may also beexerted without hindering the effects of the constituent elements.

As for the inorganic oxide particles in the photocatalytic layer, thenumber average particle diameter calculated by the measurement of thelength of arbitrary 100 particles within a visual field of a scanningelectron microscope with 200,000× magnification is preferably 5 nm ormore and less than 40 nm, more preferably more than 5 nm and 20 nm orless.

By using the inorganic oxide particles of the average particle diameterof less than 40 nm, more preferably 20 nm or less, the gas permeabilityin the photocatalytic layer and gas decomposition reactivity isincreased, and the abrasion resistance is increased.

Furthermore, making the inorganic oxide particles have a number averageparticle diameter of 5 nm or more and less than 40 nm, more preferablymore than 5 nm and 20 nm or less, can be suitably combined with each ofthe constituent elements of the present invention described up to here,and new effects mentioned above may also be exerted without hinderingthe effects of the constituent elements.

The photocatalytic layer may comprise a surfactant as an optionalcomponent. The surfactant used in the present invention may be comprisedin the photocatalytic layer as an optional component in an amount of 0part by mass or more and less than 10 parts by mass, preferably 0 partby mass or more and 8 parts by mass or less, more preferably 0 or moreand 6 parts by mass or less, relative to the total amount of 100 partsby mass of the photocatalytic particles, the inorganic oxide particles,and the hydrolyzable silicone. One of the effects of the surfactant isleveling property to the substrate. In applications where the levelingeffect is necessary, such as coating in a large area, amount of thesurfactant may be determined in the aforementioned range as neededdepending on the combination of the coating liquid and the substrate.The lower limit in this case is preferably 0.1 part by mass relative tothe total amount of 100 parts by mass of the photocatalytic particles,the inorganic oxide particles, and the hydrolyzable silicone. Althoughthe surfactant is an effective component to improve the wettability ofthe photocatalytic coating liquid, it is equivalent to the inevitableimpurity which no longer contributes to the effect of thephotocatalyst-coated body of the present invention in the photocatalyticlayer formed after applying and drying. Therefore, the upper limitshould be less than 10 parts by mass, preferably less than 8 parts bymass, more preferably 6 parts by mass or less, relative to the totalamount of 100 parts of the photocatalytic particles, inorganic oxideparticles, and the hydrolyzable silicone. That is, the surfactant may beused in the aforementioned range of the amount depending on thewettability required for the photocatalytic coating liquid. It is mostpreferable that the surfactant is virtually or definitely not comprisedin applications where the wettability is not required. The surfactant tobe used may be selected from nonionic surfactant, anionic surfactant,cationic surfactant, and amphoteric surfactant as needed considering thedispersion stability of the photocatalyst and the inorganic oxideparticles and the wettability when applied on the intermediate layer.Among these a nonionic surfactant is especially preferable, among whichmore preferable are ether-type nonionic surfactant, ester-type nonionicsurfactant, polyalkylene glycol-type nonionic surfactant, fluorine-typenonionic surfactant, and silicone-based nonionic surfactant.

Furthermore, making the surfactant used in the present invention becomprised in the photocatalytic layer as an optional component in anamount of 0 part by mass or more and less than 10 parts by mass,preferably 0 part by mass or more and 8 parts by mass or less, morepreferably 0 or more and 6 parts by mass or less, relative to the totalamount of 100 parts by mass of the photocatalytic particles, theinorganic oxide particles and the hydrolyzable silicone can be suitablycombined with each of the constituent elements of the present inventiondescribed up to here, and new effects mentioned above may also beexerted without hindering the effects of the constituent elements.

It is preferable that the photocatalytic layer has a film thickness of0.5 μm or more and 3.0 μm or less, more preferably 1.0 μm or more and2.0 μm or less. By using the photocatalytic layer of the film thicknessof 0.5 μm or more, more preferably 1.0 μm or more, weather resistance isincreased because the ultraviolet light reaching the interface of thephotocatalytic layer and the substrate is sufficiently attenuated. Inaddition, harmful gas decomposability is also increased because amountof the photocatalytic particles, the content of which is lower than theinorganic oxide particles, can be increased in the direction of the filmthickness. Furthermore, excellent characteristics in transparency andfilm strength can be attained by using the photocatalytic layer of thefilm thickness of 3.0 μm or less, more preferably 2.0 μm or less.

Furthermore, making the film thickness of the photocatalytic layer 0.5μm or more and 3.0 μm or less, more preferably 1.0 μm or more and 2.0μm, can be suitably combined with each of the constituent elements ofthe present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

The photocatalytic layer may further comprise a hydrolyzedcondensation-polymerization product of titanium alkoxide or a derivativeof titanium alkoxide as an optional component in an amount of 0 part bymass or more and less than 10 parts by mass, preferably 0 part by massor more and less than 8 parts by mass, more preferably less than 6 partsby mass, in terms of titanium dioxide.

If the photocatalytic layer comprises the hydrolyzedcondensation-polymerization product of titanium alkoxide or thederivative of titanium alkoxide in an amount as small as less than 10parts by mass, preferably less than 8 parts by mass, more preferablyless than 6 parts by mass, in terms of titanium dioxide, abrasionresistance slightly increases and curing of the photocatalytic layer maybe expected in shorter time after coating compared with the hydrolyzablesilicone. However, it is preferable that the interstices between theparticles of the photocatalytic layer are sufficiently maintained inorder to take advantage of the photocatalytic gas decompositioncharacteristics of the present invention such as the excellent abilityto decompose NOx. If the hydrolyzed condensation-polymerization productof titanium alkoxide or the derivative of titanium alkoxide is used inan amount as large as 10 parts by mass or more in terms of titaniumdioxide, it is considered that such interstices between the particlesare densely filled, similarly to the case where a large amount of ahydrolyzable silicone commonly used as a binder for the photocatalyticlayer is used, resulting in prevention of the diffusion of gases. On theother hand, since the photocatalytic layer of the present embodimentdoes not comprise the hydrolyzed condensation-polymerization product oftitanium alkoxide or the derivative of titanium alkoxide or, even if itcomprises some, the content is less than 10 parts by mass relative tothe total amount of 100 parts by mass of the photocatalytic particles,the inorganic oxide particles, and the dried substance of titaniumalkoxide in terms of titanium dioxide, interstices between the particlescan be sufficiently maintained and secured, and thus attain a structurewhich facilitates diffusion of the harmful gases such as NOx and SOxinto the photocatalytic layer. As a result, it is considered that theharmful gases effectively contact with the photocatalytic particles andare decomposed by the photocatalytic activity.

Considering the aforementioned function and effect, as a more preferredconstituent in the present embodiment, it is preferable that the sum ofthe amount of the hydrolyzed condensation-polymerization product oftitanium alkoxide or the derivative of titanium alkoxide in terms oftitanium dioxide and the amount of the dried substance of thehydrolyzable silicone in terms of silica is 0 part by mass or more andless than 10 parts by mass, preferably 0 part by mass or more and lessthan 8 parts by mass, more preferably 0 part by mass or more and lessthan 6 parts by mass. It is the most preferable that the amount of thehydrolyzed condensation-polymerization product of titanium alkoxide orthe derivative of titanium alkoxide in terms of titanium dioxide isvirtually 0 part by mass.

In addition, making the photocatalytic layer further comprise thehydrolyzed condensation-polymerization product of titanium alkoxide orthe derivative of titanium alkoxide as an optional component in anamount of 0 part by mass or more and less than 10 parts by mass,preferably 0 part by mass or more and less than 8 parts by mass, morepreferably less than 6 parts by mass in terms of titanium dioxide; morepreferably making the sum of the amount of the hydrolyzedcondensation-polymerization product of titanium alkoxide or thederivative of titanium alkoxide in terms of titanium dioxide and theamount of the dried substance of the hydrolyzable silicone in terms ofsilica 0 part by mass or more and less than 10 parts by mass, preferably0 part by mass or more and less than 8 parts by mass, more preferably 0part by mass or more and less than 6 parts by mass; and making theamount of the hydrolyzed condensation-polymerization product of titaniumalkoxide or the derivative of titanium alkoxide in terms of titaniumdioxide virtually 0 part by mass can be suitably combined with each ofthe constituent elements of the present invention described up to here,and new effects mentioned above may also be exerted without hinderingthe effects of the constituent elements.

It is preferable that the photocatalytic layer is obtained by heatdrying at 200° C. or lower. Accordingly, deterioration of the substrateassociated with heating is effectively prevented when the substrate is aresin.

In addition, obtaining the photocatalytic layer by heat drying at 200°C. or lower can be suitably combined with each of the constituentelements of the present invention described up to here, and new effectsmentioned above may also be exerted without hindering the effects of theconstituent elements.

It is preferable that the hydrolyzable silicone is an organosiloxanehaving at least one reactive group selected from a group of alkoxygroups, halogen groups, and hydrogen group.

Since these hydrolyzable silicones harden by dehydrativecondensation-polymerization by drying at ambient temperature or heattreatment at 10° C. or higher and 500° C. or lower to give a rigid driedsubstance of the hydrolyzable silicone, the abrasion resistance can beincreased.

As the hydrolyzable silicone, a silicone (oligomer and polymer) having areactive group at its end which is obtained by polymerizing abifunctional silane, trifunctional silane, or tetrafunctional silane asits monomer unit singly or in combination can be advantageously used.Among these, a silicate obtained by polymerizing a tetrafunctionalsilane unit (SiX₄, X is at least one reactive group selected from agroup of alkoxy groups, halogen groups, or hydrogen group) only(hereinafter referred to as tetrafunctional silicone) is the mostpreferable. Using the tetrafunctional silicone is preferable because thehydrophilicity of the photocatalytic layer is good and self-cleaningproperty is exerted at the same time. As the tetrafunctional silicone,an alkyl silicate such as methyl silicate, ethyl silicate, and isopropylsilicate can be advantageously used.

In addition, making the hydrolyzable silicone an organosiloxane havingat least one reactive group selected from a group of alkoxy groups,halogen groups, and hydrogen group; using the silicone (oligomer andpolymer) having a reactive group at its end which is obtained bypolymerizing a bifunctional silane, trifunctional silane, ortetrafunctional silane preferably as its monomer unit singly or incombination, as the hydrolyzable silicone; and more preferably using thetetrafunctional silicone can be suitably combined with each of theconstituent elements of the present invention described up to here, andnew effects mentioned above may also be exerted without hindering theeffects of the constituent elements.

It is more preferable that the hydrolyzable silicone is anorganosiloxane having an alkoxy group. The organosiloxane having analkoxy group enables more controllable dehydrativecondensation-polymerization reaction compared with the organosiloxanehaving a halogen or hydrogen group and is likely to give aphotocatalytic layer with a stable quality.

In addition, making the hydrolyzable silicone the organosiloxane havingan alkoxy group can be suitably combined with each of the constituentelements of the present invention described up to here, and new effectsmentioned above may also be exerted without hindering the effects of theconstituent elements.

It is more preferable that the dried substance of the hydrolyzablesilicone is a hydrolytic condensation-polymerization product of thehydrolyzable silicone.

The hydrolytic condensation-polymerization reaction is more controllablecompared with other radical polymerization reaction and the like and islikely to give a photocatalytic layer with a stable quality.

In addition, making the dried substance of the hydrolyzable silicone thehydrolytic condensation-polymerization product of the hydrolyzablesilicone can be suitably combined with each of the constituent elementsof the present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

Substrate

The substrate usable in the present invention may be various materialson which the photocatalyst layer can be formed, regardless of an organicmaterial or an inorganic material, and the shape of the substrate is notlimited. Preferable examples of substrates in view of material includemetals, ceramics, glasses, plastics, rubbers, stones, cements,concretes, fibers, fabrics, woods, papers, combinations of these,laminations of these, and ones having at least one coated layer on thesurface of these. Preferable examples of substrates in view ofapplication include building materials; building exterior materials;window frames; window glasses; structural members; exterior componentsand coating of vehicles; exterior components of machines; apparatus andgoods; dustproof masks and coating; traffic signs; various types ofdisplays; advertising pillars; road sound barriers; railway soundbarriers; bridges; exterior components and coating of crash barriers;inner walls and coating of tunnels; insulators; solar cell covers;heat-collecting covers for solar water heaters; plastic greenhouses;vehicle lamp covers; outdoor lighting apparatus; pedestals; and variousexterior materials such as films, sheets and seals to be attached to thesurfaces of the above articles.

According to a preferred aspect of the present invention, the substratemay have at least the surface composed of an organic material, andinclude a substrate entirely made of an organic material and a substratemade of an inorganic material of which the surface is covered with anorganic material (e.g., decorative plate). According to thephotocatalyst layer of the present invention, corrosion does not easilyoccur in an organic material, which is sensitive to the photocatalystactivity, a photocatalyst-coated body having superior functions can beproduced by use of the photocatalyst layer alone without an intermediatelayer. As a result, since there is no necessity to form the intermediatelayer, it is possible to save time and cost required for manufacturingphotocatalyst-coated bodies.

In addition, using the substrate having at least a surface formed of anorganic material as the substrate can be suitably combined with each ofthe constituent elements of the present invention described up to here,and new effects mentioned above may also be exerted without hinderingthe effects of the constituent elements.

An embodiment in which the photocatalytic layer is directly coated onthe substrate can also exert the features of the present invention moresufficiently, because the photocatalytic layer of the present inventionis excellent in adaptability to the surface irregularity and the like ofthe substrate, since the photocatalytic layer of the present inventionis mainly composed of particles.

In addition, making the photocatalytic layer directly coated on thesubstrate can be suitably combined with each of the constituent elementsof the present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

It is also preferable that an intermediate layer is provided between thesubstrate and the photocatalytic layer. Especially by utilizing asubstance excellent in weather resistance as the intermediate layer, theweather resistance can be increased when the substrate is a resin. Asthe substance excellent in weather resistance, a silicone-containingresin and a fluorine-containing resin are especially preferable. Inaddition, utilizing a substance excellent in flexibility as theintermediate layer is preferable because poor appearance due to thecracks and the like is unlikely to occur in use even if the substratehas irregularity. As the substance excellent in flexibility used for theintermediate layer, a resin having a double chain structure, a resinhaving a cyclic structure, a silicone having a bifunctional monomerunit, and a silicone having both of organic and inorganic crosslinks areespecially preferable.

In addition, providing the intermediate layer between the substrate andthe photocatalytic layer; using the substance excellent in weatherresistance as the intermediate layer; using at least one of thesilicone-comprising resin and the fluorine-comprising resin as thesubstance excellent in weather resistance; using the substance excellentin flexibility as the intermediate layer; and using at least one of theresin having a double chain structure, the resin having a cyclicstructure, the silicone having a bifunctional monomer unit, and thesilicone having both of organic and inorganic crosslinks as thesubstance excellent in flexibility can be suitably combined with each ofthe constituent elements of the present invention described up to here,and new effects mentioned above may also be exerted without hinderingthe effects of the constituent elements.

The intermediate layer preferably comprises a silicone-modified resinand, more preferably, an acrylic silicone.

In this way, the weather resistance of the intermediate layer,durability against the photocatalytic reaction, flexibility and the likecan be sufficiently exerted.

As the silicone-modified resin, a silicone-modified acrylic resin, asilicone-modified epoxy resin, a silicone-modified urethane resin, asilicone-modified polyester, etc. which include polysiloxane in theresin are more preferable from the point of weather resistance.

It is preferable that the silicone-modified resin comprises silicon atomin an amount of 0.2% by mass or more and less than 16.5% by mass, morepreferably 6.5% by mass or more and less than 16.5% by mass relative tothe solid content of the silicone-modified resin. If the silicon atomcontent comprised in the silicone-modified resin is 0.2% by mass ormore, the weather resistance of the intermediate layer is good and thepossibility of erosion by the photocatalyst is suppressed. If thesilicon atom content comprised in the silicone-modified resin is lessthan 16.5% by mass, sufficient flexibility is attained and occurrence ofcracks in the intermediate layer is suppressed. The silicon atom contentin the aforementioned silicone-modified resin can be measured by thechemical analysis using an X-ray electronic spectroscopic analyzer(XPS).

In addition, it is more preferable that two fluids of thesilicone-modified acrylic resin having a carboxyl group and the siliconeresin having an epoxy group are mixed and used as the acrylic silicone,from a point of increasing the strength of the coated film.

Although the dry film thickness of the intermediate layer is notparticularly limited, it is preferably 1 μm to 50 μm, more preferably 1μm to 10 μm. If the film thickness is less than 1 μm, the effect torestrict the deterioration of the intermediate layer and the substrateby the photocatalyst may be meager. If the film thickness is more than50 μm, fine cracks may occur after drying, depending on the type of theintermediate layer.

In addition, making the intermediate layer comprise thesilicone-modified resin; making the silicone-modified resin comprisesilicon atom in an amount of 0.2% by mass or more and less than 16.5% bymass, more preferably 6.5% by mass or more and less than 16.5% by mass;making the intermediate layer comprise the acrylic silicone; preferablymixing two fluids of the silicone-modified acrylic resin having acarboxyl group and the silicone resin having an epoxy group to be usedas the acrylic silicone; and making the dry film thickness of theintermediate layer preferably 1 μm to 50 μm, more preferably 1 μm to 10μm, can be suitably combined with each of the constituent elements ofthe present invention described up to here and can exert new effectsmentioned above without hindering the effects of the constituentelements.

It is preferable that the intermediate layer comprises an ultravioletabsorption agent. In this way, the weather resistance and the durabilityagainst the photocatalytic reaction of the substrate can be furtherincreased.

In addition, making the intermediate layer comprise the ultravioletabsorption agent can be suitably combined with each of the constituentelements of the present invention described up to here and can exert neweffects mentioned above without hindering the effects of the constituentelements.

The intermediate layer preferably comprises an organic antifungal agent.By virtue of the organic antifungal agent comprised in the intermediatelayer different from the photocatalytic layer as well as the intersticesprovided between the particles of the photocatalytic layer, theantialgal and antifungal function of the photocatalyst and the antialgaland antifungal function of the organic antifungal agent can beeffectively exerted without mutual deterioration.

In addition, making the intermediate layer comprise the organicantifungal agent can be suitably combined with each of the constituentelements of the present invention described up to here and can exert neweffects mentioned above without hindering the effects of the constituentelements.

The intermediate layer may further comprise additives for paint such asorganic solvent, colored pigment, body pigment, pigment dispersant,antifoaming agent, antioxidant, and the like and other componentsusually comprised in the paint. In addition, silica microparticles maybe comprised as a matting agent.

The aforementioned colored pigment is not particularly limited and, forexample, inorganic pigments such as titanium dioxide, iron oxide, carbonblack and the like and organic pigments such as phthalocyanine series,benzimidazolone series, is oindolinone series, azo series, anthraquinoneseries, quinophthalone series, anthrapyridinine series, quinacridoneseries, toluidine series, pyrathrone series, perylene series, and thelike may be used.

Although the coated body of the present invention is applicable to bothof exterior and interior materials, it is preferably used for exteriormaterials because the sunlight can be used as the light source for thephotocatalyst. As the exterior material, architectural material,exterior of buildings, window frame, window glass, structural member,exterior and coating of vehicle, exterior of machines and articles,cover and coating for dust prevention, traffic signs, various displayapparatus, advertising pillar, sound insulation wall for road, soundinsulation wall for railway, bridge, exterior and coating for guardrail, interior and coating for tunnel, insulator, cover for solar cell,heat collection cover for solar water heater, greenhouse, cover forvehicle illuminating lamp, exterior lighting apparatus, rack, and film,sheet, seal, etc. to adhere on the aforementioned articles areexemplified.

In addition, using the coated body as an exterior material can besuitably combined with each of the constituent elements of the presentinvention described up to here and can exert new effects mentioned abovewithout hindering the effects of the constituent elements.

Furthermore, at least one metal and/or metal compound comprising themetal selected from a group composed of vanadium, iron, cobalt, nickel,manganese, palladium, zinc, ruthenium, rhodium, platinum and gold may beadded in the photocatalytic layer. In this way, the catalytic functionof these metals may be expressed simultaneously.

Photo-Crystal Layer and Photo-Crystal Coating Liquid for Forming it

The photocatalyst layer according to the present invention comprises 1part or more and less than 20 parts by mass of photocatalyst particles,70 parts or more and less than 99 part by mass of inorganic oxideparticles, zero parts or more and less than 10 parts by mass of ahydrolyzable silicone, and zero parts or more and less than 10 parts bymass of a surfactant. The total amount of the photocatalyst particles,the inorganic oxide particles and the hydrolyzable silicone is 100 partsby mass. The photocatalyst layer can be formed by coating the substratewith a photocatalyst coating liquid comprising a solvent and a solutecomprising the above-described constituents in the above-described massratio dispersed in the solvent.

According to a preferred aspect of the present invention, the filmthickness of the photocatalyst layer is preferably 0.5 μm to 3.0 μm,more preferably 1.0 μm to 2.0 μm. Within this film-thickness range,ultraviolet light reaching the interface between the photocatalyst layerand the substrate is sufficiently attenuated, leading to an improvementin weather resistance. In addition, it is possible to increase theamount of photocatalyst particles positioned in the film-thicknessdirection although the content ratio of the photocatalyst particle islower than that of the inorganic oxide particles, resulting in animprovement in noxious gas decomposability. Further, superior propertiesin ultraviolet absorptivity, transparency and film strength can beprovided.

The photocatalyst particles usable in the present invention are notparticularly limited as far as they have photocatalyst activity, andparticles of various types of photocatalysts can be used. Examples ofthe photocatalyst particles include metal-oxide particles such asparticles of titanium oxide (TiO₂), ZnO, SnO₂, SrTiO₃, WO₃, Bi₂O₃, andFe₂O₃, preferably titanium oxide particles, more preferably anatasetitanium oxide particles. The titanium oxide is harmless, chemicallystable and available in low cost. Because of its high band gap energy,the titanium oxide needs ultraviolet light for photoexcitation and doesnot absorb visible light in the process of the photoexcitaiton. As aresult, coloration by complementary color components does not occur. Thetitanium oxide is available in various forms such as powder, sol, andsolution. Any form of titanium oxide may be employed as far as itexhibits photocatalyst activity. According to a preferred aspect of thepresent invention, the photocatalyst particles preferably have anaverage particle size of 10 nm to 100 nm, more preferably 10 nm to 60nm. The average particle size is calculated as a number average valueobtained by measuring the lengths of 100 particles randomly selectedfrom the particles located within a visible field magnified 200,000times by a scanning electron microscope. The most suitable shape of theparticle is a perfect sphere, but an approximately round or ellipticalparticle may be employed, in which case the length of the particle isapproximately calculated as ((long diameter+short diameter)/2). Withinthis range, the weather resistance, the noxious gas decomposability, andthe desired coating properties (such as ultraviolet absorptivity,transparency and film strength) are effectively exhibited. When acommercially available photocatalyst of sol form is used and processedso that the particle diameter becomes 30 nm or less, preferably 20 nm orless, it is also possible to produce a photocatalyst layer withespecially high transparency.

The content of the photocatalyst particles in the photocatalyst layer orthe coating liquid of the present invention is 1 part or mote and lessthan 20 parts by mass, preferably 5 parts to 15 parts by mass, morepreferably 5 parts to 10 parts by mass with respect to the total 100parts by mass of the photocatalyst particles, the inorganic oxideparticles and the hydrolyzable silicone. Since the proportion of thephotocatalyst particles is set to be low as described above, directcontact of the photocatalyst particles with the substrate is reduced asmuch as possible, thus suppressing corrosion of the substrate (inparticular the organic material). As a result, it is supposed that theweather resistance is also improved. Nevertheless, the functions of thenoxious gas decomposability and the ultraviolet absorptivity to becaused by photocatalyst activity can be also effectively exhibited.

According to a preferred aspect of the present invention, titania may beadded to the photocatalyst layer or the photocatalyst coating liquid,together with at least one metal selected from the group consisting ofvanadium, iron, cobalt, nickel, palladium, zinc, ruthenium, rhodium,lead, copper, silver, platinum and gold and/or a metallic compound ofthese metals, in order to improve the photocatalytic ability. Thisaddition can be conducted in accordance with either a method of adding asolution containing a photocatalyst and the above-described metal ormetallic compound as it is or a method of using the photocatalysis redoxreaction to allow the metal or metallic compound to be supported on thephotocatalyst.

The inorganic oxide particles employed in the present invention is notparticularly limited as long as they are capable of being combined withthe photocatalyst particles to form a layer, and any type of inorganicoxide particles may be employed. Examples of such inorganic oxideparticles include particles of a single oxide such as silica, alumina,zirconia, ceria, yttria, boronia, magnesia, calcia, ferrite, amorphoustitania and hafnia; and particles of a composite oxide such as bariumtitanate and calcium silicate, preferably silica particles. Theseinorganic oxide particles preferably are in an aqueous colloid form withwater as a dispersion medium or in an organosol form of a colloidaldispersion in a hydrophilic solvent such as ethyl alcohol, isopropylalcohol or ethylene glycol, and colloidal silica is particularlypreferable. According to a preferred aspect of the present invention,the average particle size of the inorganic oxide particles is preferably10 nm or more and less than 40 nm, more preferably 10 nm to 30 nm. Theaverage particle size is calculated as a number average value obtainedby measuring the lengths of 100 particles randomly selected from theparticles located within a visible field magnified 200,000 times by ascanning electron microscope. The most suitable shape of the particle isa perfect sphere, but an approximately round or elliptical particle maybe employed, in which case the length of the particle is approximatelycalculated as ((long diameter+short diameter)/2). Within this range, theweather resistance, the noxious gas decomposability, and the desiredcoating properties (such as ultraviolet absorptivity, transparency andfilm strength) are effectively exhibited. In particular, it is alsopossible to produce a transparent photocatalyst layer with especiallyhigh adhesion.

The content of the inorganic oxide particles in the photocatalyst layeror the coating liquid of the present invention is 70 parts or more andless than 99 parts by mass, preferably 80 parts to 95 parts by mass,more preferably 85 parts to 95 parts by mass, further preferably 90parts to 95 parts by mass, with respect to the total 100 parts by massof the photocatalyst particles, the inorganic oxide particles and thehydrolyzable silicone.

The photocatalyst layer of the present invention preferably issubstantially free from the hydrolyzable silicone, more preferablycompletely free from the hydrolyzable silicone. The hydrolyzablesilicone is a generic name for organosiloxane having an alkoxy groupand/or a partial hydrolysis condensate of the organosiloxane. However,the hydrolyzable silicone may be added as an optional component to sucha level that the noxious gas decomposability of the present inventioncan be ensured. Accordingly, the hydrolyzable silicone content is, on asilica basis, zero parts or more and less than 10 parts by mass,preferably 5 parts or less by mass, most preferably zero parts by mass,with respect to the total 100 parts by mass of the photocatalystparticles, the inorganic oxide particles and the hydrolyzable silicone.A tetrafunctional silicone compound is frequently used as a hydrolyzablesilicone, and is commercially available, for example, as ethylsilicate40 (oligomer, R is an ethyl group), ethylsilicate 48 (oligomer, R is anethyl group), methylsilicate 51 (oligomer, R is methyl group), all ofwhich are produced by Colcoat Co. Ltd.

The surfactant usable in the present invention may be added to thephotocatalyst layer in an amount of zero parts or more by mass and lessthan 10 parts by mass as an optional component, preferably zero parts to8 parts by mass, more preferably zero parts to 6 parts by mass. One ofthe effects of the surfactant is the leveling properties to thesubstrate. Therefore, the amount of surfactant may be appropriatelydetermined within the aforementioned range, depending on a combinationof the coating liquid and the substrate. In this case, the lower limitof the content of the surfactant may be 0.1 parts by mass. Thesurfactant is a component effective for improving the coating propertiesof the photocatalyst coating liquid. In the photocatalyst layer formedafter being coated, however, the surfactant corresponds to unavoidableimpurities which do not contribute to the benefits provided by thephotocatalyst-coated body of the present invention. Accordingly, thesurfactant can be employed within in the above content range dependingon coating properties required for the photocatalyst coating liquid. Ifcoating properties are not considered, substantially no or completely nosurfactant may be comprised. A surfactant to be used may be suitablychosen in view of dispersion stability of photocatalyst or inorganicoxide particles or coating properties when the coating is applied to anintermediate layer. Preferred examples of the surfactant includenonionic surfactants, more preferably ether-type nonionic surfactants,ester-type nonionic surfactants, poly-alkylene glycol-type nonionicsurfactants, fluorinated nonionic surfactants, and silicon-basednonionic surfactants.

The photocatalyst coating liquid of the present invention can beobtained by dispersing the photocatalyst particles, the inorganic oxideparticles, and optionally the hydrolyzable silicone and the surfactant,into a solvent in the aforementioned specific proportion. Any type ofsolvent may be employed in which the above-described constituents can beappropriately dispersed, and may be water or an organic solvent. Thesolid concentrations of the photocatalyst coating liquid of the presentinvention are not particularly limited, but is preferably 1 mass % to 10mass % for coating easily. Analysis of the constituents in thephotocatalyst composition can be conducted by using ultrafiltration toseparate the coating liquid into particle components and a filtrate tobe respectively analyzed in infrared spectroscopic analysis, gelpermeation chromatography, X-ray fluorescence spectrochmeical analysisor the like for spectral analysis.

Manufacturing Process

The photocatalyst-coated body of the present invention can be readilymanufactured by applying the photocatalyst coating liquid of the presentinvention to the substrate. Application of the photocatalyst layer canbe conducted in accordance with conventional methods, which includesbrush application, roller, spraying, roll coater, flow coater, dipcoating, screen printing, electrolytic deposition, vapor deposition, andthe like. The coating liquid after applied to the substrate may be driedat room temperature or, if needed, may be dried by heating. Since thephotocatalyst layer of the photocatalyst-coated body of the presentinvention is less likely to corrode organic materials, which arevulnerable to photocatalyst activity, it is possible to use aphotocatalyst layer alone without an intermediate layer to produce aphotocatalyst-coated body having the superior functions. It is thereforepossible to save time and cost required for manufacturingphotocatalyst-coated bodies due to no necessity to form the intermediatelayer.

EXAMPLES

The present invention will be described in detail with reference to thefollowing Examples, but the present invention is not limited to theseExamples.

The raw materials used to produce a photocatalyst coating liquid in thefollowing Examples will be described below.

Photocatalyst Particles

Titania aqueous dispersion (average particle diameter: 30 nm to 60 nm,basic)

Inorganic Oxide Particles

Aqueous dispersion-type colloidal silica (produced by Nissan ChemicalIndustrials Ltd., trade name: SNOWTEX 50, particle diameter: 20 nm to 30nm, solids content: 48%) (used in Examples 1 to 19 and Examples 24 to27)Aqueous dispersion-type colloidal silica (produced by Nissan ChemicalIndustrials Ltd., trade name: SNOWTEX 40, particle diameter: 10 nm to 20nm, solids content: 40%) (used in Example 20)Aqueous dispersion-type colloidal silica (produced by Nissan ChemicalIndustrials Ltd., trade name: SNOWTEX 50, particle diameter: 20 nm to 30nm, solids content: 48%) (used in Example 21)Aqueous dispersion-type colloidal silica (produced by Nissan ChemicalIndustrials Ltd., trade name: SNOWTEX S, particle diameter: 8 nm to 11nm, solids content: 30%) (used in Example 22)Aqueous dispersion-type colloidal silica (produced by Nissan ChemicalIndustrials Ltd., trade name: SNOWTEX XS, particle diameter: 4 nm to 6nm, solids content: 20%) (used in Example 23)

Hydrolyzable Silicone

Polycondensate of tetramethoxysilane (produced by Tama Chemicals Co.,Ltd., trade name: M silicate 51)

Surfactant

Polyether modified silicone surfactant (produced by Shin-Etsu ChemicalCo., Ltd., trade name: silicone-modified polyether (KF-643))

Examples 1-7 Evaluation of Weather Resistance

A photocatalyst-coated body having a photocatalyst layer was produced asfollows. A colored organic coated body was prepared as a substrate. Thecolored organic coated body was obtained by coating a float plate glasswith a general-purposed acrylic silicone with a carbon black powderadded, and then sufficiently drying and curing it. On the other hand, aphotocatalyst coating liquid was prepared by mixing a titania aqueousdispersion as a photocatalyst, an aqueous dispersion-type colloidalsilica as an inorganic oxide, water as a solvent, and apolyether-modified silicone surfactant all together in the proportionsshown in Table 1. It should be noted that the photocatalyst coatingliquid does not include the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalyst coating liquid was 5.5% by mass.

The photocatalyst coating liquid thus obtained was applied, by spraycoating, to the colored organic coated body which has been previouslyheated to 50° C. The photocatalyst coating liquid was then dried for 5minutes at 120° C. In this way, a photocatalyst layer was formed toobtain a photocatalyst-coated body. When the film thickness of thephotocatalyst layer was measured with a scanning electron microscope,the film thickness was about 0.5 μm in each of Examples 1 to 7.

A weathering test was conducted on the photocatalyst-coated body thusobtained with the size of 50 mm×100 mm as described below. Thephotocatalyst-coated body was placed in a sunshine weather meter(produced by SUGA TEST INSTRUMENTS CO., LTD., S-300C) in accordance withJIS B7753. After a lapse of 300 hours, a test piece was taken out tomeasure a color difference before and after the accelerated test withColor Meter ZE2000 produced by Nippon Denshoku Instruments Co., Ltd. Thevalues Δb of the measurement were compared to evaluate the degree ofcolor change.

The results are shown in Table 1 and FIG. 1, in which “G” means that thecolor showed little change and “NG” means that the values Δb becamepositive (yellow discoloration). As shown in Table 1 and FIG. 1, it hasbeen found that the photocatalyst-coated body has sufficient weatherresistance by setting the photocatalyst content in the photocatalystlayer to less than 20 parts by mass, preferably 15 parts or less bymass, even when the photocatalyst layer is formed on the organicsubstrate.

TABLE 1 Titanium oxide Example particles Silica particles Surfactant(part No. (part by mass) (part by mass) by mass) Δb 1 1 99 6 G 2 5 95 6G 3 10 90 6 G 4 15 85 6 G 5 18 82 6 G  6* 20 80 6 NG  7* 30 70 6 NG*Comparative Examples

Examples 8-11 Evaluation of Noxious Gas Decomposability

A photocatalyst-coated body having a photocatalyst layer was produced asfollows. A colored organic coated body was prepared as a substrate. Thecolored organic coated body was obtained by coating a float plate glasswith a general-purposed acrylic silicone with carbon black powder added,and then sufficiently drying and curing it. On the other hand, aphotocatalyst coating liquid was prepared by mixing a titania aqueousdispersion as a photocatalyst, an aqueous dispersion-type colloidalsilica as an inorganic oxide, water as a solvent, a polyether-modifiedsilicone surfactant, and a polycondensate of tetramethoxysilane as ahydrolyzable silicone all together in the proportions shown in Table 2.It should be noted that the photocatalyst coating liquids in Examples 8and 10 do not include the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalyst coating liquid was 5.5% by mass.

The photocatalyst coating liquid thus obtained was applied, by spraycoating, to the colored organic coated body which has been previouslyheated to 50° C. The photocatalyst coating liquid was then dried for 5minutes at 120° C. In this way, a photocatalyst layer was formed toobtain a photocatalyst-coated body. When the film thickness (μm) of thephotocatalyst layer was measured with a scanning electron microscope,the film thickness was about 1 μm in each of Examples 8 to 11.

A gas decomposition test was conducted on the photocatalyst-coated bodythus obtained with the size of 50 mm×100 mm as described below. As apretreatment, the photocatalyst-coated body was irradiated with BLBlight at 1 mW/cm² for 12 hours or more. The coated body sample wasplaced in a reactor in accordance with JIS R1701. Air adjusted to 50% RHat 25° C. was mixed with NO gas to a level about 1000 ppb, and wasintroduced to the light-shielded reactor for 20 minutes. With the gasbeing introduced, the BLB light was applied at 3 mW/cm² for 20 minutes.The reactor was then shielded from light again in a condition where thegas is introduced. The amount of NOx removed was calculated from the NOconcentrations and the NO₂ concentrations before and after theirradiation with the BLB light, in accordance with the followingequation:

The amount of NOx removed=[NO (after BLB irradiation)−NO (at BLBirradiation)]−[NO₂ (at BLB irradiation)−NO₂ (after BLB irradiation)]

The results are shown in Table 2, in which “G” means that the amount ofNOx removed is 400 ppb or more and “NG” means that the amount of NOxremoved is 10 ppb or less. As shown in Table 2, it has been found thatsatisfactory NOx decomposition was demonstrated by the photocatalystlayer comprising the photocatalyst particles and the inorganic oxide andbeing substantially free from the hydrolyzable silicone. On the otherhand, it has been found that the photocatalyst layer comprising 10 partsby mass of the hydrolyzable silicone lost NOx decomposability.

TABLE 2 Titanium oxide Silica Hydrolyzable Surfactant NOx removal Ex.particles (PBM) particles (PBM) Silicone (PBM) (PBM) amount  8 10 90 0 6G (461 ppb)  9* 10 80 10 6 NG (2 ppb)     10 15 85 0 6 G (532 ppb) 11 1580 5 6 G (441 ppb) PBM: Part by mass *Comparative Example.

Examples 12-19 Measurement of Linear Transmittance and UV Shielding Rate

A photocatalyst-coated body having a photocatalyst layer was produced asfollows. A float plate glass of 94% transmittance at the wavelength of550 nm was prepared as a substrate. On the other hand, a photocatalystcoating liquid was prepared by mixing a titania aqueous dispersion as aphotocatalyst, an aqueous dispersion-type colloidal silica as aninorganic oxide having an average particle diameter ranging from 20 nmto 30 nm, water as a solvent, and a polyether-modified siliconesurfactant all together in the proportions shown in Table 3. It shouldbe noted that the photocatalyst coating liquid does not include thehydrolyzable silicone. The total solid concentration of thephotocatalyst and the inorganic oxide in the photocatalyst coatingliquid was 5.5% by mass.

The photocatalyst coating liquid thus obtained was applied, by spraycoating, to the colored organic coated body which has been previouslyheated to 50° C. The photocatalyst coating liquid was then dried for 5minutes at 120° C. In this way, a photocatalyst layer was formed toobtain a photocatalyst-coated body. When the film thickness (μm) of thephotocatalyst layer was measured with a scanning electron microscope,values were obtained as shown in Table 3.

Measurements of linear transmittance at 550 nm and ultraviolet (300 nm)shielding rate were conducted on a photocatalyst-coated body with thesize of 50 mm×100 mm as described below by use of an UV/VIS/NIRspectrophotometer (produced by Shimadzu Corporation, UV-3150).

The results are shown in Table 3 and FIGS. 2 and 3. Evaluation on lineartransmittance and ultraviolet shielding rate was conducted according tothe following criteria.

<Linear Transmittance>

A: linear transmittance at 550 nm is 97% or moreB: linear transmittance at 550 nm is 95% or more and less than 97%C: linear transmittance at 550 nm is less than 95%<

<UV Shielding Rate>

A: UV (300 nm) shielding rate is 80% or moreB: UV (300 nm) shielding rate is 30% or more and less than 80%C: UV (300 nm) shielding rate is less than 30%

As shown in Table 3, FIG. 2 and FIG. 3, it has been found that it ispossible to sufficiently shield the ultraviolet, which causesdegradation of the organic substance, and to ensure transparency, bysetting the film thickness to 3 μm or less when the content of thephotocatalyst in the photocatalyst layer ranges from 5 parts to 15 partsby mass.

TABLE 3 Titanium UV oxide Silica Surfac- Film Linear shielding particlesparticles tant thickness transmittance rate Ex. (PBM) (PBM) (PBM) (μm)(550 nm) (300 nm) 12 5 95 6 0.5 A B 13 5 95 6 1.5 A B 14 10 90 6 0.5 A B15 10 90 6 1.5 A A 16 5 95 6 3 B A 17 10 90 6 3 B A 18 1 99 6 0.5 A C 191 99 6 1.5 A C PBM: Part by mass

Examples 20-23 Measurement of Haze

A photocatalyst-coated body having a photocatalyst layer was produced asfollows. A float plate glass of 94% transmittance at the wavelength of550 nm was prepared as a substrate. On the other hand, a photocatalystcoating liquid was prepared by mixing a titania aqueous dispersion as aphotocatalyst, an aqueous dispersion-type colloidal silica as aninorganic oxides having various average particle diameters shown inTable 4, water as a solvent, and a polyether-modified siliconesurfactant all together in the proportions shown in Table 4. It shouldbe noted that the photocatalyst coating liquid does not comprise thehydrolyzable silicone. The total solid concentration of thephotocatalyst and the inorganic oxide in the photocatalyst coatingliquid was 5.5% by mass.

The photocatalyst coating liquid thus obtained was applied to theabove-described substrate by spin coating at 1000 rpm for 10 seconds,and then dried for 5 minutes at 120° C. to form a photocatalyst layer.Haze was measured on a photocatalyst-coated body with the size of 50mm×100 mm thus obtained by use of a haze meter (produced by GardnerCorporation, haze-gard plus).

The results are shown in Table 4. As shown in Table 4, it has been foundthe haze value can be reduced to less than 1% so that transparency canbe ensured, by setting the particle diameter of the metallic oxideparticles in the photocatalyst layer to 10 nm to 30 nm.

TABLE 4 Titanium oxide Silica Silica particle particles particlesdiameter Surfactant Haze Ex. (PBM) (PBM) (nm) (PBM) (%) 20 10 90 10-20 60.68 21 10 90 20-30 6 0.48 22 10 90  8-11 6 1.11 23 10 90 4-6 6 1.22PBM: Part by mass

Examples 24-27 Evaluation of Influence by Surfactant Addition

A photocatalyst-coated body having a photocatalyst layer was produced asfollows. A colored organic coated body was prepared as a substrate. Thecolored organic coated body was obtained by coating a float plate glasswith a general-purposed acrylic silicone with a carbon black powderadded, and then sufficiently drying and curing it. On the other hand, aphotocatalyst coating liquid was prepared by mixing a titania aqueousdispersions as a photocatalyst, an aqueous dispersion-type colloidalsilica as an inorganic oxide, water as a solvent, and apolyether-modified silicone surfactant all together in the proportionsshown in Table 5. It should be noted that the photocatalyst coatingliquid does not comprise the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalyst coating liquid was 5.5% by mass.

The photocatalyst coating liquid thus obtained was applied, by spraycoating, to the colored organic coated body which has been previouslyheated to 50° C. to 60° C. The photocatalyst coating liquid was driedfor 5 minutes at 120° C. In this way, a photocatalyst layer was formedto obtain a photocatalyst-coated body. When the film thickness (μm) ofthe photocatalyst layer was measured with a scanning electronmicroscope, the film thickness was about 1 μm in each of Examples 24 to27.

A gas decomposition test was conducted on the photocatalyst-coated bodythus obtained with the size of 50 mm×100 mm as described below. As apretreatment, the photocatalyst-coated body was irradiated with BLBlight at 1 mW/cm² for 12 hours or more. The coated body sample wasplaced in a reactor in accordance with JIS R1701. Air adjusted to 50% RHat 25° C. was mixed with NO gas to a level about 1000 ppb, and wasintroduced to the light-shielded reactor for 20 minutes. With the gasbeing introduced, the BLB light was applied at 3 mW/cm² for 20 minutes.The reactor was then shielded from light again in a condition where thegas is introduced. The amount of NOx removed was calculated from the NOconcentrations and the NO₂ concentrations before and after theirradiation with the BLB light, in accordance with the followingequation:

The amount of NOx removed=[NO (after BLB irradiation)−NO (at BLBirradiation)]−[NO₂ (at BLB irradiation)−NO₂ (after BLB irradiation)]

The results are shown in Table 5, in which the NOx removal efficienciesare shown relatively to the removal efficiency 100 in Example 25. Asshown in Table 5, it has been found that increasing the amount of thesurfactant leads to reduction in removal efficiency.

TABLE 5 Titanium oxide Silica NOx removal particles particles Surfactantefficiencies Ex. (PBM) (PBM) (PBM) (Ex. 25 is 100) 24  10 90 0 98 25  1090 6 100 26* 10 90 10 85 27* 10 90 33.3 79 PBM: Part by mass.

Additional embodiments of the present invention involving a lowercontent of photocatalytic particles are discussed below, i.e., exampleshaving 5 parts by mass or less of photocatalytic particles.

Photocatalytic Coating Liquid

The photocatalytic coating liquid according to the present invention isa coating liquid for forming the aforementioned photocatalyst-coatedbody and comprises a solvent, the photocatalytic particles having anaverage particle diameter of 10 nm or more and 100 nm or less in anamount of 1 part by mass or more and 5 parts by mass or less, theinorganic oxide particles in an amount of more than 85 parts by mass and99 parts by mass or less, and the hydrolyzable silicone in an amount of0 part by mass or more and less than 10 parts by mass in terms ofsilica, so that the total amount of the photocatalytic particles, theinorganic oxide particles and the hydrolyzable silicone in terms ofsilica is 100 parts by mass.

That is, when the photocatalytic layer is formed by applying and dryingthe photocatalytic coating liquid on the substrate, it is consideredthat considerably lower content of the photocatalytic particles than theinorganic oxide particles (specifically, more than 1 part by mass andless than 5 parts by mass, preferably 2 parts by mass or more and lessthan 5 parts by mass, more preferably 2 parts by mass or more and 4.5part by mass or less relative to the total amount of 100 parts by massof the photocatalytic particles, inorganic oxide particles andhydrolyzable silicone) enables to minimize the direct contact of thephotocatalytic particles with the substrate, thereby resulting in lowtendency of erosion of the substrate (especially the organic substrate).In addition, it is considered that deterioration of the substrate byultraviolet light can be reduced by reducing the dose of the ultravioletlight reaching the substrate since the photocatalyst itself absorbs theultraviolet light.

At the same time, by this construction, it becomes possible to obtain aphotocatalyst-coated body excellent in harmful gas decomposability andvarious desired coating characteristics (such as transparency and filmstrength), while preventing erosion of the substrate (especially theorganic substrate). First of all, the photocatalytic layer is basicallycomposed of two types of particles, i.e., photocatalytic particles andinorganic oxide particles, resulting in the plentiful presence ofinterstices between the particles. If a large amount of hydrolyzablesilicone which is commonly used as a binder of the photocatalytic layeris used, it is considered that the gas diffusion is hindered becausesuch interstices between the particles are densely filled. However,since the photocatalytic layer of the present invention does notcomprise the dried substance of the hydrolyzable silicone or, even if itcomprises some, the content is less than 10 parts by mass relative tothe total amount of 100 parts by mass of the photocatalytic particles,the inorganic oxide particles, and the dried substance of thehydrolyzable silicone in terms of silica, interstices between theparticles can be sufficiently maintained and secured and facilitatediffusion of the harmful gases such as NOx and SOx into thephotocatalytic layer. As a result, it is considered that the harmfulgases effectively contact with the photocatalytic particles and aredecomposed by the photocatalytic activity. Considering theaforementioned action and effect, it is the most preferable that theamount of the dried substance of the hydrolyzable silicone in terms ofsilica is virtually 0 part by mass.

In particular, in the aforementioned construction, the photocatalyticparticles can exert photocatalytic decomposition function such as afunction to decompose NOx in an amount as small as more than 1 part bymass and less than 5 parts by mass. Therefore, it is considered that aphotocatalyst-coated body excellent in weather resistance,hydrophilicity, harmful gas decomposability and various desired coatingcharacteristics (such as transparency and film strength) is realized,while preventing erosion of the substrate (especially the organicsubstrate). Accordingly, the photocatalytic layer of the presentinvention can exert excellent durability even with high ultraviolet doseand under hot and humid weather conditions in tropical and subtropicalregions especially at low latitudes, at the same time as thephotocatalytic decomposition function.

It is preferable that the average particle diameter of thephotocatalytic particles in the photocatalytic coating liquid is 10 nmor more and 100 nm or less, more preferably 10 nm or more and 60 nm orless. The average particle diameter is calculated as a number averagevalue of the measured length of arbitrary 100 particles within a visualfield of a scanning electron microscope with 200,000× magnification.Although the most preferred shape of the particle is perfect sphere,approximate circle or ellipse may be acceptable, in which case thelength of the particle is approximately calculated as ((major axis+minoraxis)/2). In this range, gas permeation amount in the photocatalyticlayer formed by applying and drying the photocatalytic coating liquid onthe substrate, specific surface area for sufficient gas decompositionactivity, monocrystalline size for sufficient photocatalytic activity ofthe particle, and various coating film characteristics such astransparency and weather resistance can be exerted in a balanced manner.Furthermore, making the average particle diameter of the photocatalyticparticles 10 nm or more and 100 nm or less, more preferably 10 nm ormore and 60 nm or less can be suitably combined with each of theconstituent elements of the present invention described up to here, andnew effects mentioned above may also be exerted without hindering theeffects of the constituent elements.

As the photocatalytic particles, particles of metal oxide such astitanium oxide (TiO₂), ZnO, SnO₂, SrTiO₃, WO₃, Bi₂O₃, and Fe₂O₃ areexemplified. Any metal oxides exemplified here can be suitably combinedwith each constituent elements of the present invention described up tohere.

As the photocatalytic particles in the photocatalytic coating liquid,titanium oxide particles are preferable. Titanium oxide has better waterresistance compared with ZnO and exerts better photocatalytic functioncompared with SnO₂ such as gas decomposition by the light of thewavelength of 380 nm to 420 nm which is included sufficiently insunlight. Furthermore, microparticles of a nanometer order of titaniumoxide are more available than SrTiO₃, therefore the specific surfacearea is large and practically sufficient photocatalytic activity isattainable. Furthermore, due to its larger bandgap compared with WO₃,Bi₂O₃, and Fe₂O₃, titanium oxide has a sufficient oxidation power,prevents recoupling of conductive electron and positive hole afterphotoexcitation, and has activation energy sufficient for gasdecomposition. In addition, titanium oxide is harmless, chemicallystable, and available at low cost. In addition, due to its high bandgapenergy, titanium oxide needs ultraviolet light for photoexcitation anddoes not absorb visible light in the process of photoexcitation,resulting in no coloration by complementary color component.

Titanium oxide is available in various forms such as powder, sol,solution, etc., and titanium oxide in any form may be added into thecoating liquid as long as it shows photocatalytic activity afterapplying and drying on the substrate.

Using titanium oxide particles as the photocatalytic particles can besuitably combined with each of the constituent elements of the presentinvention described up to here, and new effects mentioned above may alsobe exerted without hindering the effects of the constituent elements.

As the photocatalytic particles in the photocatalytic coating liquid,anatase-type titanium oxide is preferable among titanium oxideparticles. Anatase-type titanium oxide has an oxidation power strongerthan rutile-type titanium oxide and exerts stronger photocatalyticfunction such as gas decomposition. Furthermore, using anatase-typetitanium oxide particles as the photocatalytic particles can be suitablycombined with each of the constituent elements of the present inventiondescribed up to here, and new effects mentioned above may also beexerted without hindering the effects of the constituent elements.

It is preferable that Cu component is further incorporated into thephotocatalytic coating liquid. Cu itself has excellent antifungalcharacteristics and excellent adsorption characteristics for harmfulgases and acts on the photocatalytic particles to decrease theprobability of recoupling of conductive electron and positive holegenerated by photoexcitation of the photocatalyst, resulting inincreasing the oxidation power and gas decomposition power of thephotocatalytic particles. Larger effect is exerted if the photocatalystis a photocatalyst having intrinsically strong oxidation power, such astitanium oxide, especially anatase-type titanium oxide.

Incorporating Cu component into the photocatalytic coating liquid can besuitably combined with each of the constituent elements of the presentinvention described up to here, and new effects mentioned above may alsobe exerted without hindering the effects of the constituent elements.

It is preferable that Cu component is supported on the photocatalyticparticles in the photocatalytic coating liquid. Not only simplyincorporating the Cu component but also making the Cu componentpositively supported on the photocatalytic particles can act on thephotocatalytic particles to decrease the probability of recoupling ofconductive electron and positive hole generated by photoexcitation ofthe photocatalyst and thus increase the oxidation power of thephotocatalytic particles, further facilitating the effect of increasinggas decomposition power. Larger effect is exerted if the photocatalystis a photocatalyst having intrinsically strong oxidation power, such astitanium oxide, especially anatase-type titanium oxide. Furthermore,making Cu positively supported on the photocatalytic particles can besuitably combined with each of the constituent elements of the presentinvention described up to here, and new effects mentioned above may alsobe exerted without hindering the effects of the constituent elements.

It is preferable that both of the Cu component and the Ag component areboth incorporated into the photocatalytic coating liquid. Incorporatingboth of Cu and Ag into the photocatalytic coating liquid not only exertsthe excellent antifungal characteristics of Cu and excellentantibacterial characteristics of Ag simultaneously, but substantiallyincreases the decomposition activity of the photocatalyst. Although themechanism is not clear at present, mutual interactions among thephotocatalytic particles, Ag, and Cu are presumably correlated. Largereffect is exerted if the photocatalyst is a photocatalyst havingintrinsically strong oxidation power, such as titanium oxide, especiallyanatase-type titanium oxide. Furthermore, incorporating both of the Cucomponent and the Ag component into the photocatalytic coating liquidcan be suitably combined with each of the constituent elements of thepresent invention described up to here, and new effects mentioned abovemay also be exerted without hindering the effects of the constituentelements.

It is preferable that both of the Cu component and the Ag component aresupported on the photocatalytic particles in the photocatalytic coatingliquid. Not only making Cu and Ag present in the photocatalytic coatingliquid but also making Cu and Ag positively supported on thephotocatalytic particles can act on the photocatalytic particles todecrease the probability of recoupling of conductive electron andpositive hole generated by photoexcitation of the photocatalyst and thusincrease the oxidation power of the photocatalytic particles, furtherfacilitating the effect of increasing gas decomposition power. Largereffect is exerted if the photocatalyst is a photocatalyst havingintrinsically strong oxidation power, such as titanium oxide, especiallyanatase-type titanium oxide. Furthermore, making both of Cu and Agpositively supported on the photocatalytic particles can be furthersuitably combined with each of the constituent elements of the presentinvention described up to here, and new effects mentioned above may alsobe exerted without hindering the effects of the constituent elements.

As the inorganic oxide particles in the photocatalytic coating liquid,for example, particles of single oxide such as silica, alumina,zirconia, ceria, yttria, boronia, magnesia, calcia, ferrite, iron oxide,amorphous titania, hafnia, tin oxide, manganese oxide, niobium oxide,nickel oxide, cobalt oxide, indium oxide, lanthanum oxide, barium oxide,etc.; or complex oxide such as aluminosilicate, barium titanate, calciumsilicate, etc. can be suitably used. These inorganic oxide particles arepreferably added in the form of an aqueous colloid in water as adispersant or an organosol dispersed in a form of colloid in ahydrophilic solvent such as ethyl alcohol, isopropyl alcohol, orethylene glycol and the like.

It is considered that mixing the inorganic oxide particles in thephotocatalytic coating liquid can moderately decrease the amount of thephotocatalyst and minimize the direct contact of the photocatalyticparticles with the substrate, while securing the gas permeability in thephotocatalytic layer obtained by applying and drying the photocatalyticcoating liquid, thereby preventing the erosion of the substrate(especially the organic substrate). In addition, it is considered thatdeterioration of the substrate by ultraviolet light can be reduced byreducing the dose of the ultraviolet light reaching the substrate sincethe photocatalyst itself absorbs the ultraviolet light.

As the inorganic oxide particles in the photocatalytic coating liquid,silica is the most preferable. Incorporating silica increases thehydrophilicity of the photocatalytic layer, which is washed by water orrainwater, resulting in effectively preventing the stain adhered to thesurface from decreasing the decomposition function of the photocatalyst.This preventive effect is especially enhanced if the photocatalyst is aphotocatalyst having intrinsically strong oxidation power, such astitanium oxide, especially anatase-type titanium oxide. The silicaparticles are preferably in the form of an aqueous colloid in water as adispersant or an organosol dispersed in a form of colloid in ahydrophilic solvent such as ethyl alcohol, isopropyl alcohol, orethylene glycol and the like, especially preferably being colloidalsilica. Furthermore, using silica particles as the inorganic oxideparticles can be suitably combined with each of the constituent elementsof the present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

As for the inorganic oxide particles in the photocatalytic coatingliquid, the number average particle diameter calculated by themeasurement of the length of arbitrary 100 particles within a visualfield of a scanning electron microscope with 200,000× magnification ispreferably 5 nm or more and less than 40 nm, more preferably more than 5nm and 20 nm or less.

Using the inorganic oxide particles with the average particle diameterof less than 40 nm, more preferably 20 nm or less, improves the gaspermeability, the gas decomposition reactivity and the abrasionresistance in the photocatalytic layer obtained by applying and dryingthe photocatalytic coating liquid on the substrate

Furthermore, making the inorganic oxide particles in the photocatalyticcoating liquid have a number average particle diameter of 5 nm or moreand less than 40 nm, more preferably more than 5 nm and 20 nm or less,can be suitably combined with each of the constituent elements of thepresent invention described up to here, and new effects mentioned abovemay also be exerted without hindering the effects of the constituentelements.

The photocatalytic coating liquid may comprise a surfactant as anoptional component. The surfactant used in the present invention may becomprised in the photocatalytic layer as an optional component in anamount of 0 part by mass or more and less than 10 parts by mass,preferably 0 part by mass or more and 8 parts by mass or less, morepreferably 0 or more and 6 parts by mass or less, relative to the totalamount of 100 parts by mass of the photocatalytic particles, theinorganic oxide particles, and the hydrolyzable silicone. One of theeffects of the surfactant is leveling property to the substrate. In thecase where the leveling effect is necessary, such as coating in a largearea, amount of the surfactant may be determined in the aforementionedrange as needed depending on the combination of the coating liquid andthe substrate. The lower limit in this case is preferably 0.1 part bymass relative to the total amount of 100 parts by mass of thephotocatalytic particles, the inorganic oxide particles, and thehydrolyzable silicone. Although the surfactant is an effective componentto improve the wettability of the photocatalytic coating liquid, it isequivalent to the inevitable impurity which no longer contributes to theeffect of the photocatalyst-coated body of the present invention in thephotocatalytic layer formed after applying and drying. Therefore, theupper limit should be less than 10 parts by mass, preferably less than 8parts by mass, more preferably 6 parts by mass or less, relative to thetotal amount of 100 parts of the photocatalytic particles, inorganicoxide particles, and the hydrolyzable silicone. That is, the surfactantmay be used in the aforementioned range of the content depending on thewettability required for the photocatalytic coating liquid. It is mostpreferable that the surfactant is virtually or definitely not comprisedfor the application where the wettability is not required. Thesurfactant to be used may be selected from nonionic surfactant, anionicsurfactant, cationic surfactant, and amphoteric surfactant as neededconsidering the dispersion stability of the photocatalyst and theinorganic oxide particles and the wettability when applied on theintermediate layer. Among these a nonionic surfactant is especiallypreferable, among which more preferable are ether-type nonionicsurfactant, ester-type nonionic surfactant, polyalkylene glycol-typenonionic surfactant, fluorine-type nonionic surfactant, andsilicone-based nonionic surfactant.

Furthermore, as for the surfactant used in the coating liquid of thepresent invention, making the surfactant comprised in the photocatalyticlayer as an optional component in an amount of 0 part by mass or moreand less than 10 parts by mass, preferably 0 part by mass or more and 8parts by mass or less, more preferably 0 or more and 6 parts by mass orless, relative to the total amount of 100 parts by mass of thephotocatalytic particles, the inorganic oxide particles, and thehydrolyzable silicone can be suitably combined with each of theconstituent elements of the present invention described up to here, andnew effects mentioned above may also be exerted without hindering theeffects of the constituent elements.

The photocatalytic coating liquid may further comprise a hydrolyzedcondensation-polymerization product of titanium alkoxide or a derivativeof titanium alkoxide as an optional component in an amount of 0 part bymass or more and less than 10 parts by mass, preferably 0 part by massor more and less than 8 parts by mass, more preferably less than 6 partsby mass, in terms of titanium dioxide.

If the photocatalytic coating liquid comprises the hydrolyzedcondensation-polymerization product of titanium alkoxide or thederivative of titanium alkoxide in an amount as small as less than 10parts by mass, preferably less than 8 parts by mass, more preferablyless than 6 parts by mass, in terms of titanium dioxide, abrasionresistance slightly increases and curing of the photocatalytic layer maybe expected in shorter time after coating compared with the hydrolyzablesilicone. However, it is preferable that the interstices between theparticles of the photocatalytic layer are sufficiently maintained inorder to take advantage of the photocatalytic gas decompositioncharacteristics of the present invention such as the excellent abilityto decompose NOx. If the hydrolyzed condensation-polymerization productof titanium alkoxide or the derivative of titanium alkoxide is used inan amount as large as 10 parts by mass or more in terms of titaniumdioxide, it is considered that such interstices between the particlesare densely filled to prevent the diffusion of gases, similarly to thecase where a hydrolyzable silicone commonly used as a binder for thephotocatalytic layer is used in a large amount. On the other hand, sincethe photocatalytic coating liquid of the present embodiment does notcomprise the hydrolyzed condensation-polymerization product of titaniumalkoxide or the derivative of titanium alkoxide or, even if it comprisessome, the amount is less than 10 parts by mass relative to the totalamount of 100 parts by mass of the photocatalytic particles, theinorganic oxide particles, and the dried substance of titanium alkoxidein terms of titanium dioxide, it is considered to be possible tomaintain and secure interstices between the particles, which attain astructure where the harmful gases such as NOx and SOx are easilydiffused into the photocatalytic layer. As a result, it is consideredthat the harmful gases effectively contact with the photocatalyticparticles and are decomposed by the photocatalytic activity.

Considering the aforementioned action and effect, as a more preferredconstruction in the present embodiment, it is preferable that the sum ofthe amount of the hydrolyzed condensation-polymerization product oftitanium alkoxide or the derivative of titanium alkoxide in terms oftitanium dioxide and the amount of the dried substance of thehydrolyzable silicone in terms of silica is 0 part by mass or more andless than 10 parts by mass, preferably 0 part by mass or more and lessthan 8 parts by mass, more preferably 0 part by mass or more and lessthan 6 parts by mass. It is the most preferable that the amount of thehydrolyzed condensation-polymerization product of titanium alkoxide orthe derivative of titanium alkoxide in terms of titanium dioxide isvirtually 0 part by mass.

In addition, making the photocatalytic coating liquid further comprisethe hydrolyzed condensation-polymerization product of titanium alkoxideor the derivative of titanium alkoxide as an optional component in anamount of 0 part by mass or more and less than 10 parts by mass,preferably 0 part by mass or more and less than 8 parts by mass, morepreferably less than 6 parts by mass in terms of titanium dioxide;making the sum of the amount of the hydrolyzedcondensation-polymerization product of titanium alkoxide or thederivative of titanium alkoxide in terms of titanium dioxide and theamount of the dried substance of the hydrolyzable silicone in terms ofsilica 0 part by mass or more and less than 10 parts by mass, preferably0 part by mass or more and less than 8 parts by mass, more preferably 0part by mass or more and less than 6 parts by mass; and making theamount of the hydrolyzed condensation-polymerization product of titaniumalkoxide or the derivative of titanium alkoxide in terms of titaniumdioxide virtually 0 part by mass can be suitably combined with each ofthe constituent elements of the present invention described up to here,and new effects mentioned above may also be exerted without hinderingthe effects of the constituent elements.

It is preferable that the hydrolyzable silicone, which is an optionalcomponent in the photocatalytic coating liquid, is an organosiloxanehaving at least one reactive group selected from the group consisting ofalkoxy group, halogen group, and hydrogen group.

Since these hydrolyzable silicones, after applying to the substrate,harden by dehydrative condensation-polymerization by drying at ambienttemperature or heat treatment at 10° C. or higher and 500° C. or lowerto give a rigid dried substance of the hydrolyzable silicone, so thatthe abrasion resistance can be increased.

As the hydrolyzable silicone, a silicone having a reactive group at itsend which is obtained by polymerizing a bifunctional silane,trifunctional silane, or tetrafunctional silane as its monomer unitsingly or in combination (oligomer and polymer) can be advantageouslyused. Among these, a silicate obtained by polymerizing a tetrafunctionalsilane unit (SiX₄, X is at least one reactive group selected from thegroup consisting of alkoxy group, halogen group, or hydrogen group) only(hereinafter referred to as tetrafunctional silicone) is the mostpreferable. Using the tetrafunctional silicone is preferable because thehydrophilicity of the photocatalytic layer is good and self-cleaningproperty is exerted at the same time. As the tetrafunctional silicone,an alkyl silicate such as methyl silicate, ethyl silicate, and isopropylsilicate can be advantageously used.

In addition, making the hydrolyzable silicone, which is an optionalcomponent in the photocatalytic coating liquid, an organosiloxane havingat least one reactive group selected from the group consisting of alkoxygroup, halogen group, and hydrogen group; using the silicone (oligomerand polymer) having a reactive group at its end which is preferablyobtained by polymerizing a bifunctional silane, trifunctional silane, ortetrafunctional silane as its monomer unit singly or in combination asthe hydrolyzable silicone; and more preferably using the tetrafunctionalsilicone can be suitably combined with each of the constituent elementsof the present invention described up to here, and new effects mentionedabove may also be exerted without hindering the effects of theconstituent elements.

It is more preferable that the hydrolyzable silicone, which is anoptional component in the photocatalytic coating liquid, is anorganosiloxane having an alkoxy group. The organosiloxane having analkoxy group makes it easier to control dehydrativecondensation-polymerization reaction, compared with the organosiloxanehaving a halogen or hydrogen group, and to form a photocatalytic layerwith a stable quality.

In addition, making the hydrolyzable silicone, which is an optionalcomponent in the photocatalytic coating liquid, the organosiloxanehaving an alkoxy group can be suitably combined with each of theconstituent elements of the present invention described up to here, andnew effects mentioned above may also be exerted without hindering theeffects of the constituent elements.

Furthermore, at least one metal selected from a group consisting ofvanadium, iron, cobalt, nickel, manganese, palladium, zinc, ruthenium,rhodium, platinum and gold and/or a metal compound the metal may beadded into the photocatalytic coating liquid. In this way, the catalyticfunctions of these metals may be exerted simultaneously. The additioncan be performed by any method such as mixing and dissolving ordispersing the metal or metal compound to the coating liquid, or makingthe metal or metal compound supported on the photocatalytic layer orphotocatalytic particles.

As a solvent in the photocatalytic coating liquid, both of water andorganic solvent may be used, water being preferable. In this way, thecoating film can be formed without volatilization of the organic solventat coating, which is preferable from the standpoint of environment. Inaddition, although the solid concentration of the photocatalytic coatingliquid of the present invention is not particularly limited, 1 to 10% bymass is preferable because of easiness of coating. In addition, theconstituent of the photocatalytic coating composition can be analyzed byseparating the coating liquid into the particle component and thefiltrate by ultrafiltration, followed by individual analysis by infraredspectroscopic analysis, gel permeation chromatography, fluorescent X-rayspectroscopy, etc. and analysis of the spectrum.

In addition, using water as the solvent for the photocatalytic coatingliquid; and making the solid concentration of the photocatalytic coatingliquid 1 to 10% by mass can be suitably combined with each of theconstituent elements of the present invention described up to here andcan exert new effects mentioned above without hindering the effects ofthe constituent elements.

Among the aforementioned photocatalyst-coated bodies, the coating liquidfor forming the intermediate layer to form the photocatalyst-coated bodyprovided with the intermediate layer preferably comprises a solvent anda silicone-modified resin, more preferably a solvent and an acrylicsilicone.

In this way, the weather resistance, durability against thephotocatalytic reaction, flexibility and the like of the intermediatelayer can be sufficiently exerted.

As the silicone-modified resin, a silicone-modified acrylic resin, asilicone-modified epoxy resin, a silicone-modified urethane resin, asilicone-modified polyester, etc. which include polysiloxane in theresin are more preferable from the point of weather resistance.

It is preferable that the silicone-modified resin comprises silicon atomin an amount of 0.2% by mass or more and less than 16.5% by mass, morepreferably 6.5% by mass or more and less than 16.5% by mass relative tothe solid content of the silicone-modified resin. If the silicon atomcontent comprised in the silicone-modified resin is 0.2% by mass ormore, the weather resistance of the intermediate layer is good and thepossibility of erosion by the photocatalyst is suppressed. If thesilicon atom content comprised in the silicone-modified resin is lessthan 16.5% by mass, sufficient flexibility is attained and occurrence ofcracks in the intermediate layer is suppressed. The silicon atom contentin the aforementioned silicone-modified resin can be measured by thechemical analysis using an X-ray photoelectron spectroscopic analyzer(XPS).

In addition, it is more preferable that two fluids of thesilicone-modified acrylic resin having a carboxyl group and the siliconeresin having an epoxy group are mixed and used as the acrylic silicone,from a point of increasing the strength of the coated film.

In addition, making the intermediate layer comprise thesilicone-modified resin; making the silicone-modified resin comprisesilicon atom in an amount of 0.2% by mass or more and less than 16.5% bymass, more preferably 6.5% by mass or more and less than 16.5% by mass;making the intermediate layer comprise the acrylic silicone; and mixingand using two fluids of the silicone-modified acrylic resin having acarboxyl group and the silicone resin having an epoxy group as theacrylic silicone can be suitably combined with each of the constituentelements of the present invention described up to here and can exert neweffects mentioned above without hindering the effects of the constituentelements.

In addition, making the coating liquid for forming the intermediatelayer comprise the solvent and the silicone-modified resin; and makingthe coating liquid for forming the intermediate layer comprise thesolvent and the acrylic silicone can be suitably combined with each ofthe constituent elements of the present invention described up to hereand can exert new effects mentioned above without hindering the effectsof the constituent elements.

Among the aforementioned photocatalyst-coated bodies, the coating liquidfor forming the intermediate layer to form the photocatalyst-coated bodyprovided with the intermediate layer preferably comprises an ultravioletabsorption agent. In this way, the weather resistance and the durabilityagainst the photocatalytic reaction of the substrate can be furtherincreased.

In addition, making the coating liquid for forming the intermediatelayer comprise the ultraviolet absorption agent can be suitably combinedwith each of the constituent elements of the present invention describedup to here and can exert new effects mentioned above without hinderingthe effects of the constituent elements.

Among the aforementioned photocatalyst-coated bodies, the coating liquidfor forming the intermediate layer to form the photocatalyst-coated bodyprovided with the intermediate layer preferably comprises an organicantifungal agent. In virtue of the organic antifungal agent comprised inthe intermediate layer different from the photocatalytic layer as wellas the interstices provided between the particles of the photocatalyticlayer, the antialgal and antifungal function of the photocatalyst andthe antialgal and antifungal function of the organic antifungal agentcan be effectively exerted without mutual deterioration.

In addition, making the coating liquid for forming the intermediatelayer comprise the antifungal agent can be suitably combined with eachof the constituent elements of the present invention described up tohere and can exert new effects mentioned above without hindering theeffects of the constituent elements.

As a solvent in the coating liquid for forming the intermediate layer,both of water and organic solvent may be used, water being preferable.In this way, the coating film can be formed without volatilization ofthe organic solvent at coating, which is preferable from the standpointof environment.

In addition, although the solid concentration of the liquid agent forcoating the intermediate layer of the present invention is notparticularly limited, 10 to 20% by mass is preferable because ofeasiness of coating. In addition, the constituent of the coating liquidfor the intermediate layer can be analyzed by infrared spectroscopicanalysis regarding the resin components.

In addition, using water as the solvent for the coating liquid forforming the intermediate layer; and making the solid concentration ofthe liquid agent for coating the intermediate layer of the presentinvention preferably 10 to 20% by mass can be suitably combined witheach of the constituent elements of the present invention described upto here and can exert new effects mentioned above without hindering theeffects of the constituent elements.

Method for Producing the Photocatalytic Layer

The photocatalyst-coated body of the present invention can be easilyproduced by applying the photocatalytic coating liquid of the presentinvention on the substrate. As the application method of thephotocatalytic layer, commonly and widely performed methods such asbrushing, roller coating, spraying, a roll coater, a flow coater, dipcoating, flow coating, screen printing, etc. can be used. After applyingthe coating liquid on the substrate, it may be dried at ambienttemperature or by heating as needed. If the coated body is heated untilsintering is advanced, the interstices between the particles aredecreased, resulting in insufficient photocatalytic activity. In thepresent invention, the drying temperature is 10° C. or higher and 500°C. or lower. The upper limit may be determined as needed depending onthe type of the substrate. If a resin is comprised in at least a part ofthe substrate, the preferred drying temperature is 10° C. or higher and200° C. or lower, considering the allowable temperature limit of theresin, etc.

Method for Producing the Intermediate Layer

The intermediate layer coated body of the present invention can beeasily produced by applying the intermediate layer coating liquid of thepresent invention on the substrate. As the application method of theintermediate layer, commonly and widely performed methods such asbrushing, roller coating, spraying, a roll coater, a flow coater, dipcoating, flow coating, screen printing, electrocoating, vapordeposition, etc. can be used. After applying the coating liquid on thesubstrate, it may be dried at ambient temperature or by heating asneeded.

Examples Example A

The present invention is specifically illustrated based on the followingexamples. The present invention is not limited to these examples.

The raw materials used for the preparation of the photocatalytic coatingliquid in the following examples are as follows:

Photocatalytic Particles

Titania water dispersion (Average particle diameter: 42 nm, basic)

Inorganic Oxide Particles

Water dispersed colloidal silica (Average particle diameter: 14 nm,basic) (Used in Examples 101 to 107, Example 109, and Examples 111 to123)Water dispersed colloidal silica (Average particle diameter: 26 nm,basic) (Used in Example 8)Water dispersed colloidal silica (Average particle diameter: 5 nm,basic) (Used in Example 110)

Hydrolyzable Silicone

Polycondensation product of tetramethoxysilane (Concentration asconverted to SiO₂: 51% by mass, Solvent: methanol and water)

Surfactant

Polyether modified silicone type surfactant

Examples 101 to 103 Evaluation of Weather Resistance (Outdoor Exposure)

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a colored organic coated body was preparedas the substrate. This colored organic coated body had been prepared byapplying a general-purpose acrylic silicone containing carbon blackpowder on a sealer-treated siding substrate for ceramics industry,followed by sufficient drying and curing. Meanwhile, the titania waterdispersion as the photocatalyst, the water dispersed colloidal silica asthe inorganic oxide, water as the solvent, and the surfactant were mixedin the compounding ratio shown in Table 6 to obtain the photocatalyticcoating liquid. The photocatalytic coating liquid does not comprise thehydrolyzable silicone. The total solid concentration of thephotocatalyst and the inorganic oxide in the photocatalytic coatingliquid was 5.5% by mass.

The aforementioned colored organic coated body which had been heatedbeforehand was spray-coated with the photocatalytic coating liquid andwas dried at 120° C. In this way, the photocatalytic layer was formed toobtain the photocatalyst-coated body. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 101 to 103.

The photocatalyst-coated body of the size of 50×100 mm thus obtained wassubjected to outdoor exposure at the elevation angle of 20° and facingsouth using an exposure rack defined in JIS K 5600-7-6 in MiyakojimaIsland. The external appearance was confirmed by visual observationevery three months.

The results obtained are shown in Table 6. “G” in the Table representslittle change and “NG” represents occurrence of slight efflorescence. Asshown in Table 6, it was found that sufficient weather resistance can beattained by making the photocatalytic layer comprise less than 5 partsby mass of the photocatalytic particles, even if the organic substrateis painted with the photocatalytic layer in Miyakojima Island.

TABLE 6 Titanium oxide Silica Surface-active Appearance change particlesparticles agent 3 6 12 (parts by mass) (parts by mass) (parts by mass)months months months Example 101 4.5 95.5 6 G G G Example 102 10 90 6 GNG NG Example 103 20 80 6 NG NG NG

Examples 104 to 106 Evaluation of Hydrophilicity After UltravioletExposure

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a colored organic coated body was preparedas the substrate. This colored organic coated body had been prepared byapplying a general-purpose acrylic silicone containing carbon blackpowder on a float plate glass, followed by sufficient drying and curing.Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide having various averageparticle diameters shown in Table 7, water as the solvent, and thesurfactant were mixed in the compounding ratio shown in Table 7 toobtain the photocatalytic coating liquid. The photocatalytic coatingliquid does not comprise the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass.

The aforementioned colored organic coated body which had been heatedbeforehand was spray-coated with the photocatalytic coating liquid andwas dried at 120° C. In this way, the photocatalytic layer was formed toobtain the photocatalyst-coated body. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 104 to 106.

The hydrophilicity was evaluated for the photocatalyst-coated body thusobtained as follows. The photocatalyst-coated body was cured in a darkplace for 1 day and allowed to stand under the BLB light adjusted at 1mW/cm² with the photocatalyst painted surface upward for 7 days. Thecontact angle of the photocatalyst painted surface was measured by acontact angle meter (CA-X150 Type manufactured by Kyowa InterfaceScience Co., Ltd.). The measurement of the contact angle was tosubstitute hydrophilicity.

The results obtained are shown in Table 7. The evaluation criteria ofthe hydrophilicity after ultraviolet exposure are as follows.

[Hydrophilicity]

A: Contact angle less than 10°B: Contact angle 10° or more and less than 20°C: Contact angle 20° or moreAs shown in Table 7, it was found that the high hydrophilicity wassecured by using the photocatalytic layer comprising 2 parts by mass ormore of the photocatalytic particles.

TABLE 7 Titanium Silica Surface- oxide particles active particles (partsby agent Hydro- (parts by mass) mass) (parts by mass) philicity Example104 2 98 6 B Example 105 4.5 95.5 6 A Example 106 1 99 6 C

Examples 107 and 108 Evaluation of Sliding Abrasion Resistance

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a colored organic coated body was preparedas the substrate. This colored organic coated body had been prepared byapplying a general-purpose acrylic silicone containing carbon blackpowder on a slate board treated with an epoxy resin for sealing,followed by sufficient drying and curing. Meanwhile, the titania waterdispersion as the photocatalyst, the water dispersed colloidal silica asthe inorganic oxide having various average particle diameters shown inTable 8, water as the solvent, and the surfactant were mixed in thecompounding ratio shown in Table 8 to obtain the photocatalytic coatingliquid. The photocatalytic coating liquid does not comprise thehydrolyzable silicone. The total solid concentration of thephotocatalyst and the inorganic oxide in the photocatalytic coatingliquid was 5.5% by mass.

The aforementioned colored organic coated body which had been heatedbeforehand was spray-coated with the photocatalytic coating liquid andwas dried at 120° C. In this way, the photocatalytic layer was formed toobtain the photocatalyst-coated body. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 107 to 108.

The washing resistance test for the photocatalyst-coated body thusobtained was performed as follows. The test method was according to JISA6909. The photocatalyst-coated body was horizontally fixed on a testrack of a washability apparatus (Washability Tester No. 458 manufacturedby Toyo Seiki Seisaku-sho, Ltd.) with the photocatalyst painted surfacefacing upward. A pig bristle brush of a dry weight of 450 g was put onthe photocatalyst painted surface after the bristles were immersed in anaqueous soap solution of 0.5% and reciprocated 500 times. Then thephotocatalyst-coated body was removed, washed with water and dried.

After irradiating the thoroughly dried photocatalyst-coated body withBLB light adjusted at 3 mW/cm² for 24 hours, the contact angle of thephotocatalyst-painted surface was measured by a contact angle meter(CA-X150 Type manufactured by Kyowa Interface Science Co., Ltd.). Themeasurement of the contact angle was to substitute hydrophilicity.

The results obtained are shown in Table 8. The evaluation criteria ofthe sliding abrasion resistance are as follows.

[Sliding Abrasion Resistance]

A: Contact angle less than 10°B: Contact angle 10° or moreAs shown in Table 8, it was found that the photocatalyst-coated body ofExample 107 formed a strong film against sliding.

TABLE 8 Titanium oxide Silica Silica particle Surface-active Slidingparticle particle average particle agent abrasion (parts by mass) (partsby mass) diameter (nm) (parts by mass) resistance Example 107 4.5 95.514 6 A Example 108 4.5 95.5 26 6 B

Examples 109 and 110 Measurement of Haze

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a float plate glass having transmittance of94% at the wavelength of 550 nm was used as the substrate. Meanwhile,the titania water dispersion as the photocatalyst, the water dispersedcolloidal silica as the inorganic oxide having various average particlediameters shown in Table 9, water as the solvent, and the surfactantwere mixed in the compounding ratio shown in Table 9 to obtain thephotocatalytic coating liquid. The photocatalytic coating liquid doesnot comprise the hydrolyzable silicone. The total solid concentration ofthe photocatalyst and the inorganic oxide in the photocatalytic coatingliquid was 5.5% by mass.

The aforementioned substrate was spin coated by the photocatalyticcoating liquid obtained at 1000 rpm for 10 seconds, followed by dryingat 120° C. to obtain the photocatalytic layer. Haze of thephotocatalyst-coated body of the size of 50×100 mm thus obtained wasmeasured using a haze meter (Haze-Gard Plus manufactured by Paul N.Gardner Company, Inc.).

The results obtained are shown in Table 9. It was found that thephotocatalyst-coated body of Example 109 suppressed the haze to lessthan 1% and the transparency was secured.

TABLE 9 Titanium oxide Silica Silica particle Surface-active particleparticle average particle agent Haze (parts by mass) (parts by mass)diameter (nm) (parts by mass) (%) Example 109 4.5 95.5 14 6 0.62 Example110 4.5 95.5 5 6 1.25

Examples 111 to 114 Evaluation of Harmful Gas Decomposition Activity

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a colored organic coated body was preparedas the substrate. This colored organic coated body had been prepared byapplying a general-purpose acrylic silicone containing carbon blackpowder on a float plate glass, followed by sufficient drying and curing.Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, the water dispersedcolloidal silica as the inorganic oxide having various average particlediameters shown in Table 10, water as the solvent, and the surfactantwere mixed in the compounding ratio shown in Table 10 to obtain thephotocatalytic coating liquid. Therefore, the photocatalytic coatingliquid does not comprise the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass.

The aforementioned colored organic coated body which had been heatedbeforehand was spray-coated with the photocatalytic coating liquid andwas dried at 120° C. In this way, the photocatalytic layer was formed toobtain the photocatalyst-coated body. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation is shown in Table 10.

The gas decomposition activity test of thus obtainedphotocatalyst-coated body of size the 50×100 mm was performed asfollows. The photocatalyst-coated body was irradiated with BLB light of1 mW/cm² for 12 hours or more as pretreatment. One sample of the coatedbody was set in a reaction vessel described in JIS R1701. Air adjustedat 25° C. and 50% RH and mixed with NO gas so that the concentration ofthe NO was about 1,000 ppb was introduced into the light-shieldedreaction vessel for 20 minutes. Then the sample was irradiated with BLBlight adjusted at 3 mW/cm² with the introduced gas present. Then thereaction vessel was light shielded again with the introduced gaspresent. The NOx removal was calculated from the concentrations of NOand NO₂ before and after BLB light irradiation according to thefollowing equation.

NOx Removal=[NO (after irradiation)−NO (at irradiation)]−[NO₂ (atirradiation)−NO₂ (after irradiation)]

The results obtained are shown in Table 10. As shown in Table 10, it wasfound that the sufficient NOx decomposition activity was attained evenif the content of the photocatalytic particles in the photocatalyticlayer was less than 5 parts by mass.

TABLE 10 Titanium Surface- oxide Silica active NOx particle particleagent Film removal (parts by (parts by (parts by thickness (Examplemass) mass) mass) (μm) 14 = 100) Example 111 4.5 95.5 6 0.5 53 Example112 4.5 95.5 6 1 98 Example 113 2 98 6 1.5 57 Example 114 10 90 6 1 100

Examples 115 to 117 Influence of Hydrolyzable Silicone

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a colored organic coated body was preparedas the substrate. This colored organic coated body had been prepared byapplying a general-purpose acrylic silicone containing carbon blackpowder on a float plate glass, followed by sufficient drying and curing.Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,a polycondensation product of tetramethoxysilane as the hydrolyzablesilicone, and the surfactant were mixed in the compounding ratio shownin Table 11 to obtain the photocatalytic coating liquid. Thephotocatalytic coating liquid of Example 115 does not comprise thehydrolyzable silicone. The total solid concentration of thephotocatalyst and the inorganic oxide in the photocatalytic coatingliquid was 5.5% by mass.

The aforementioned colored organic coated body which had been heatedbeforehand was spray-coated with the photocatalytic coating liquid andwas dried at 120° C. In this way, the photocatalytic layer was formed toobtain the photocatalyst-coated body. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 115 to 117.

The gas decomposition activity of thus obtained photocatalyst-coatedbody of size the 50×100 mm was performed as follows. Thephotocatalyst-coated body was irradiated with BLB light of 1 mW/cm² for12 hours or more as pretreatment. One sample of the coated body was setin a reaction vessel described in JIS R1701. Air adjusted at 25° C. and50% RH and mixed with NO gas so that the concentration of the NO wasabout 1,000 ppb was introduced into the light-shielded reaction vesselfor 20 minutes. Then the sample was irradiated with BLB light adjustedat 3 mW/cm² with the introduced gas present. Then the reaction vesselwas light shielded again with the introduced gas present. The NOxremoval was calculated from the concentrations of NO and NO₂ before andafter BLB light irradiation according to the following equation.

NOx Removal=[NO (after irradiation)−NO (at irradiation)]−[NO₂ (atirradiation)−NO₂ (after irradiation)]

The results obtained are shown in Table 11. NOx removal in Example 115,in which the hydrolyzable silicone was not comprised at all, is taken as100. Other examples of 50 or more and less than 50, relative to Example115, are expressed as G and NG, respectively. As shown in Table 11, thephotocatalytic layer composed of the photocatalytic particles and theinorganic oxides and comprising essentially no hydrolyzable siliconeexhibited an excellent NOx decomposition activity. On the other hand, itwas found that the sample comprising 10 parts by mass of thehydrolyzable silicone lost the NOx decomposition activity.

TABLE 11 Titanium oxide Silica Hydrolyzable Surface-active NOx removalparticles particles Silicone agent (Example (parts by mass) (parts bymass) (parts by mass) (parts by mass) 15 = 100) Example 115 4.5 95.5 0 6 G (100) Example 116 4.5 90.5 5 6 G (84) Example 117 4.5 85.5 10 6 NG(41) 

Examples 118 and 119 Weather Resistance Test (Evaluation of SubstrateDeterioration)

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a colored organic coated body was preparedas the substrate. This colored organic coated body had been prepared byapplying a general-purpose acrylic silicone containing carbon blackpowder on a float plate glass, followed by sufficient drying and curing.Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in Table 12to obtain the photocatalytic coating liquid. The photocatalytic coatingliquid does not comprise the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass.

The aforementioned colored organic coated body which had been heatedbeforehand was spray-coated with the photocatalytic coating liquid andwas dried at 120° C. In this way, the photocatalytic layer was formed toobtain the photocatalyst-coated body. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 118 and 119.

The weather resistance test for the photocatalyst-coated body of thesize of 50×100 mm thus obtained was performed as follows. Thephotocatalyst-coated body was put into a xenon arc weather resistancetesting apparatus combined with hydrogen peroxide spray (Ci4000manufactured by Toyo Seiki Seisaku-sho Ltd.). Intensity of the xenon arcwas 80 W/m² (wavelength 300 to 400 nm). Concentration of hydrogenperoxide was 1%. Irradiation with the xenon lamp was performed at 22hours per cycle. Spraying of hydrogen peroxide was performed repeatedlyin a cycle of 3 minutes spraying and 2 minutes stopping during theinitial 2 hours. After 200 hours the sample was taken out and acellophane tape was adhered on the painted surface followed by peelingoff at once. The weather resistance was evaluated by the presence orabsence of the powder of the colored organic coating adhered to the gluesurface of the tape due to the deterioration of the coated film(chalking phenomenon).

The results obtained are shown in Table 12. “G” in the Table representsthat very little powder adhered to the glue surface of the tape. Asshown in Table 12, it was found that the photocatalyst-coated bodycomprising less than 5 parts by mass of the photocatalytic particles inthe photocatalytic layer has a sufficient weather resistance.

TABLE 12 Titanium Surface- oxide Silica active Presence or particleparticle agent absence of (parts by (parts by (parts by deterioration ofmass) mass) mass) the coated film Example 118 2 98 6 G Example 119 4.595.5 6 G

Examples 120 to 123 Measurement of Linear Transmittance

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a float plate glass having transmittance of94% at the wavelength of 550 nm was prepared as the substrate.Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in Table 13to obtain the photocatalytic coating liquid. The photocatalytic coatingliquid does not comprise the hydrolyzable silicone. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass.

The aforementioned float plate glass which had been heated beforehandwas spray-coated with the photocatalytic coating liquid and was dried at120° C. In this way, the photocatalytic layer was formed to obtain thephotocatalyst-coated body. The film thickness of the photocatalyticlayer measured by scanning electron microscopic observation is shown inTable 13.

The measurement of linear (550 nm) transmittance for thephotocatalyst-coated body of the size of 50×100 mm thus obtained wasperformed using an ultraviolet-visible-near infrared spectrophotometer(UV-3150 manufactured by Shimadzu Corporation).

The results obtained are shown in Table 13. The evaluation criteria ofthe linear transmittance are as follows.

[Linear Transmittance]

A: Linear (550 nm) transmittance 95% or moreB: Linear (550 nm) transmittance 90% or more and less than 95%

The photocatalyst-coated bodies in Table 13 showed high transparency.

TABLE 13 Titanium Surface- oxide Silica active Film Linear particleparticle agent thickness trans- (parts by (parts by (parts by (micro-mittance mass) mass) mass) meter) (550 nm) Example 120 4.5 95.5 6 0.5 BExample 121 4.5 95.5 6 1.5 B Example 122 2 98 6 0.5 A Example 123 2 98 61.5 B

Example B

The present invention is specifically illustrated based on the followingexamples. The present invention is not limited to these examples.

In the following examples, the intermediate layer coating liquid wasprepared by mixing any one of the silicone-modified acrylic resinmaterials shown below, water and a film-forming auxiliary agent asneeded. Details are shown in Table 14.

A silicone-modified acrylic resin dispersion with silicon atom contentof 10% by mass relative to the solid content of the silicone-modifiedresin

A silicone-modified acrylic resin dispersion with silicon atom contentof 0.2% by mass relative to the solid content of the silicone-modifiedresin

A silicone-modified acrylic resin dispersion with silicon atom contentof 16.5% by mass relative to the solid content of the silicone-modifiedresin

TABLE 14 Silicon atom content in the Silicone-modified acrylic resin (%by mass) M-1 10 M-2 0.2 M-3 16.5

In the following examples, the photocatalytic layer coating liquid wasprepared by mixing the photocatalytic particles shown below, any one ofthe inorganic oxides and water as needed. Details are shown in Table 15.

Photocatalytic Particles

Titania water dispersion (Average particle diameter: 42 nm, basic)

Inorganic Oxide Particles

Water dispersed colloidal silica (Average particle diameter: 14 nm,basic)Water dispersed colloidal silica (Average particle diameter: 26 nm,basic)Water dispersed colloidal silica (Average particle diameter: 5 nm,basic)

Hydrolyzable Silicone

Polycondensation product of tetramethoxysilane (concentration in termsof SiO₂: 51% by mass, Solvent: methanol and water)

Surfactant

Polyether modified silicone-based surfactant

TABLE 15 Colloidal Colloidal silica Surface- Hydrolyzable Photocatalystsilica average active silicate content content particle agent content in(parts by (parts by diameter (parts by terms of SiO₂ mass) mass) (nm)mass) (parts by mass) T-1 4.5 95.5 14 6 0 T-2 10 90 14 6 0 T-3 20 80 146 0 T-4 30 70 14 6 0 T-5 2 98 14 6 0 T-6 1 99 14 6 0 T-7 4.5 95.5 26 6 0T-8 4.5 95.5 5 6 0 T-9 4.5 90.5 14 6 5 T-10 4.5 85.5 14 6 10

Examples 131 to 133 Evaluation of Weather Resistance (Outdoor Exposure)

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a float plate glasswas prepared as the substrate. The preheated glass substrate wasspray-coated with the intermediate layer coating liquid described in M-1of Table 14 and dried at 120° C. to obtain the intermediate layer. Thesolid concentration of the resin in the M-1 solution was about 20%. Thefilm thickness of the intermediate layer measured by scanning electronmicroscopic observation was about 10 μm for any of Examples 131 to 133.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1 toT-3 of Table 15 to obtain the photocatalytic coating liquid. Thephotocatalytic coating liquid does not comprise the hydrolyzablesilicone. The total solid concentration of the photocatalyst and theinorganic oxide in the photocatalytic coating liquid was 5.5% by mass.The preheated intermediate layer coated body was spray-coated with thephotocatalytic coating liquid and was dried at 120° C. The filmthickness of the photocatalytic layer measured by scanning electronmicroscopic observation was about 0.5 μm for any of Examples 131 to 133.In this way, the intermediate layer and the photocatalytic layer wereformed to obtain the photocatalyst-coated body.

The photocatalyst-coated body of the size of 50×100 nm thus obtained wassubjected to outdoor exposure at the elevation angle of 20° and facingsouth using an exposure rack defined in JIS K 5600-7-6 in MiyakojimaIsland. The external appearance was confirmed by visual observationevery three months.

The results obtained are shown in Table 16. “G” in the Table representslittle change and “NG” represents occurrence of slight efflorescence. Asshown in Table 16, it was found that sufficient weather resistance isattained in Miyakojima Island by using the photocatalytic layercomprising less than 5 parts by mass of the photocatalyst.

TABLE 16 Intermediate Photocatalytic Appearance Change Layer Layer 3months 6 months Example 131 M-1 T-1 G G Example 132 M-1 T-2 G NG Example133 M-1 T-3 NG NG

Examples 134 to 136 Evaluation of Hydrophilicity after UltravioletExposure

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a float plate glasswas prepared as the substrate. The preheated glass substrate wasspray-coated with the intermediate layer coating liquid described in M-1of Table 14 and dried at 120° C. to obtain the intermediate layer. Thesolid concentration of the resin in the M-1 solution was about 20%. Thefilm thickness of the intermediate layer measured by scanning electronmicroscopic observation was about 10 μm for any of Examples 134 to 136.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1, T-5and T-6 of Table 15 to obtain the photocatalytic coating liquid. Thephotocatalytic coating liquid does not comprise the hydrolyzablesilicone. The total solid concentration of the photocatalyst and theinorganic oxide in the photocatalytic coating liquid was 5.5% by mass.The preheated intermediate layer coated body was spray-coated with thephotocatalytic coating liquid and was dried at 120° C. The filmthickness of the photocatalytic layer measured by scanning electronmicroscopic observation was about 0.5 μm for any of Examples 134 to 136.In this way, the intermediate layer and the photocatalytic layer wereformed to obtain the photocatalyst-coated body.

The hydrophilicity was evaluated for the photocatalyst-coated body thusobtained as follows. The photocatalyst-coated body was cured in a darkplace for 1 day and allowed to stand under the BLB light adjusted at 1mW/cm² with the photocatalyst painted surface facing upward for 7 days.The contact angle of the photocatalyst painted surface was measured by acontact angle meter (CA-X150 Type manufactured by Kyowa InterfaceScience Co., Ltd.). The measurement of the contact angle was tosubstitute hydrophilicity.

The results obtained are shown in Table 17. The evaluation criteria ofthe hydrophilicity after ultraviolet exposure are as follows.

Hydrophilicity

A: Contact angle less than 10°B: Contact angle 10° or more and less than 20°C: Contact angle 20° or more

As shown in Table 17, it was found that the high hydrophilicity wassecured by using the photocatalytic layer comprising 2 parts by mass ormore of the photocatalytic particles.

TABLE 17 Intermediate Photocatalytic layer layer Hydrophilicity Example134 M-1 T-5 B Example 135 M-1 T-1 A Example 136 M-1 T-6 C

Examples 137 and 138 Evaluation of Sliding Abrasion Resistance

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a float plate glasswas prepared as the substrate. The preheated glass substrate wasspray-coated with the intermediate layer coating liquid described in M-1of Table 14 and dried at 120° C. to obtain the intermediate layer. Thesolid concentration of the resin in the M-1 solution was about 20%. Thefilm thickness of the intermediate layer measured by scanning electronmicroscopic observation was about 10 μm for any of Examples 137 and 138.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1 andT-7 of Table 15 to obtain the photocatalytic coating liquid. Thephotocatalytic coating liquid does not comprise the hydrolyzablesilicone. The total solid concentration of the photocatalyst and theinorganic oxide in the photocatalytic coating liquid was 5.5% by mass.The preheated intermediate layer coated body was spray-coated with thephotocatalytic coating liquid and was dried at 120° C. The filmthickness of the photocatalytic layer measured by scanning electronmicroscopic observation was about 0.5 μm for any of Examples 137 and138. In this way, the intermediate layer and the photocatalytic layerwere formed to obtain the photocatalyst-coated body.

The washing resistance test for the photocatalyst-coated body thusobtained was performed as follows. The test method was according to JISA6909. The photocatalyst-coated body was horizontally fixed on a testrack of a washability apparatus (Washability Tester No. 458 manufacturedby Toyo Seiki Seisaku-sho, Ltd.) with the photocatalyst painted surfacefacing upward. A pig bristle brush of a dry weight of 450 g was put onthe photocatalyst painted surface after the bristles were immersed in anaqueous soap solution of 0.5% and reciprocated 500 times. Then thephotocatalytic painted body was removed, washed with water and dried.

After irradiating the thoroughly dried photocatalyst-coated body withBLB light adjusted at 3 mW/cm² for 24 hours, the contact angle of thephotocatalyst painted surface was measured by a contact angle meter(CA-X150 Type manufactured by Kyowa Interface Science Co., Ltd.). Themeasurement of the contact angle was to substitute hydrophilicity.

The results obtained are shown in Table 18. The evaluation criteria ofthe sliding abrasion resistance are as follows.

Sliding Abrasion Resistance

A: Contact angle less than 10°

B: Contact angle 10° or more

As shown in Table 18, it was found that the photocatalyst-coated body ofExample 137 formed a strong film against sliding.

TABLE 18 Sliding Intermediate Photocatalytic abrasion layer layerresistance Example 137 M-1 T-1 A Example 138 M-1 T-7 B

Examples 139 and 140 Measurement of Haze

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a float plate glass having transmittance of94% at the wavelength of 550 nm was used as the substrate. Meanwhile,the titania water dispersion as the photocatalyst, the water dispersedcolloidal silica as the inorganic oxide, water as the solvent, and thesurfactant were mixed in the compounding ratio shown in T-1 and T-8 ofTable 15 to obtain the photocatalytic coating liquid. The photocatalyticcoating liquid does not comprise the hydrolyzable silicone. The totalsolid concentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass.

The aforementioned substrate was spin coated by the photocatalyticcoating liquid obtained at 1000 rpm for 10 seconds, followed by dryingat 120° C. to obtain the photocatalytic layer. Haze of thephotocatalyst-coated body of the size of 50×100 mm thus obtained wasmeasured using a haze meter (Haze-Gard Plus manufactured by Paul N.Gardner Company, Inc.).

The results obtained are shown in Table 19. It was found that thephotocatalyst-coated body of Example 139 was suppressed the haze to lessthan 1% and the transparency was secured.

TABLE 19 Photocatalytic Silica particle average Haze layer particlediameter (nm) (%) Example 139 T-1 14 0.62 Example 140 T-8 5 1.25

Examples 141 to 144 Evaluation of Harmful Gas Decomposition Activity

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a float plate glasswas prepared as the substrate. The preheated glass substrate wasspray-coated with the intermediate layer coating liquid described in M-1of Table 14 and dried at 120° C. to obtain the intermediate layer. Thesolid concentration of the resin in the M-1 solution was about 20%. Thefilm thickness of the intermediate layer measured by scanning electronmicroscopic observation was about 10 μm for any of Examples 141 to 144.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1, T-2and T-5 of Table 15 to obtain the photocatalytic coating liquid. Thephotocatalytic coating liquid does not comprise the hydrolyzablesilicone. The total solid concentration of the photocatalyst and theinorganic oxide in the photocatalytic coating liquid was 5.5% by mass.The preheated intermediate layer coated body was spray-coated with thephotocatalytic coating liquid and was dried at 120° C. The filmthickness of the photocatalytic layer measured by scanning electronmicroscopic observation is shown in Table 20. In this way, theintermediate layer and the photocatalytic layer were formed to obtainthe photocatalyst-coated body.

The gas decomposition activity test of thus obtainedphotocatalyst-coated body of size the 50×100 mm was performed asfollows. The photocatalyst-coated body was irradiated with BLB light of1 mW/cm² for 12 hours or more as pretreatment. One sample of the coatedbody was set in a reaction vessel described in JIS R1701. Air adjustedat 25° C. and 50% RH and mixed with NO gas so that the concentration ofthe NO was about 1,000 ppb was introduced into the light-shieldedreaction vessel for 20 minutes. Then the sample was irradiated with BLBlight adjusted at 3 mW/cm² with the introduced gas present. Then thereaction vessel was light shielded again with the introduced gaspresent. The NOx removal was calculated from the concentrations of NOand NO₂ before and after BLB light irradiation according to thefollowing equation.

NOx Removal=[NO (after irradiation)−NO (at irradiation)]−[NO₂ (atirradiation)−NO₂ (after irradiation)]

The results obtained are shown in Table 20. As shown in Table 20, it wasfound that the sufficient NOx decomposition activity was attained evenif the content of the photocatalytic particles in the photocatalyticlayer was less than 5 parts by mass.

TABLE 20 Photo- Film Intermediate catalytic thickness NOx removal layerlayer (μm) (Example 14 = 100) Example 141 M-1 T-1 0.5 51 Example 142 M-1T-1 1 97 Example 143 M-1 T-5 1.5 56 Example 144 M-1 T-2 0.5 100

Examples 145 to 147 Influence of Hydrolyzable Silicone

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a float plate glasswas prepared as the substrate. The preheated glass substrate wasspray-coated with the intermediate layer coating liquid described in M-1of Table 14 and dried at 120° C. to obtain the intermediate layer. Thesolid concentration of the resin in the M-1 solution was about 20%. Thefilm thickness of the intermediate layer measured by scanning electronmicroscopic observation was about 10 μm for any of Examples 145 to 147.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1, T-9and T-10 of Table 15 to obtain the photocatalytic coating liquid. Thephotocatalytic coating liquid does not comprise the hydrolyzablesilicone. The total solid concentration of the photocatalyst and theinorganic oxide in the photocatalytic coating liquid was 5.5% by mass.The preheated intermediate layer coated body was spray-coated with thephotocatalytic coating liquid and was dried at 120° C. The filmthickness of the photocatalytic layer measured by scanning electronmicroscopic observation was about 0.5 μm for any of Examples 145 to 147.In this way, the intermediate layer and the photocatalytic layer wereformed to obtain the photocatalyst-coated body.

The gas decomposition activity test of thus obtainedphotocatalyst-coated body of size the 50×100 mm was performed asfollows. The photocatalyst-coated body was irradiated with BLB light of1 mW/cm² for 12 hours or more as pretreatment. One sample of the coatedbody was set in a reaction vessel described in JIS R1701. Air adjustedat 25° C. and 50% RH and mixed with NO gas so that the concentration ofthe NO was about 1,000 ppb was introduced into the light-shieldedreaction vessel for 20 minutes. Then the sample was irradiated with BLBlight adjusted at 3 mW/cm² with the introduced gas present. Then thereaction vessel was light shielded again with the introduced gaspresent. The NOx removal was calculated from the concentrations of NOand NO₂ before and after BLB light irradiation according to thefollowing equation.

NOx Removal=[NO (after irradiation)−NO (at irradiation)]−[NO₂ (atirradiation)−NO₂ (after irradiation)]

The results obtained are shown in Table 21. NOx removal in Example 145,in which the hydrolyzable silicone was not comprised at all, is taken as100. Other examples of 50 or more and less than 50, relative to Example145, are expressed as G and NG, respectively. As shown in Table 21, thephotocatalytic layer composed of the photocatalytic particles and theinorganic oxides and comprising essentially no hydrolyzable siliconeexhibited an excellent NOx decomposition activity. On the other hand, itwas found that the sample comprising 10 parts by mass of thehydrolyzable silicone lost the NOx decomposition activity.

TABLE 21 Hydrolyzed silicate Inter- Photo- content Nox removal mediatecatalytic converted to SiO₂ (Example layer layer (parts by mass) 15 =100) Example 145 M-1 T-1 0  G (100) Example 146 M-1 T-9 5 G (85) Example147 M-1  T-10 10 NG (40) 

Examples 148 to 151 Measurement of Linear Transmittance

The photocatalyst-coated body comprising the photocatalytic layer wasproduced as follows. First, a float plate glass having transmittance of94% at the wavelength of 550 nm was prepared as the substrate.Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1 andT-5 of Table 15 to obtain the photocatalytic coating liquid. Therefore,the photocatalytic coating liquid does not comprise the hydrolyzablesilicone. The total solid concentration of the photocatalyst and theinorganic oxide in the photocatalytic coating liquid was 5.5% by mass.

The aforementioned float plate glass which had been heated beforehandwas spray-coated with the photocatalytic coating liquid and was dried at120° C. In this way, the photocatalytic layer was formed to obtain thephotocatalyst-coated body. The film thickness of the photocatalyticlayer measured by scanning electron microscopic observation is shown inTable 22.

The measurement of linear (550 nm) transmittance for thephotocatalyst-coated body of the size of 50×100 mm thus obtained wasperformed using an ultraviolet-visible-near infrared spectrophotometer(UV-3150 manufactured by Shimadzu Corporation).

The results obtained are shown in Table 22. The evaluation criteria ofthe linear transmittance are as follows.

Linear Transmittance

A: Linear (550 nm) transmittance 95% or moreB: Linear (550 nm) transmittance 90% or more and less than 95%

The photocatalyst-coated bodies in Table 22 showed high transparency.

TABLE 22 Photocatalytic Film Linear Transmittance Layer Thickness (μm)(550 nm) Example 148 T-1 0.5 B Example 149 T-1 1.5 B Example 150 T-5 0.5A Example 151 T-5 1.5 B

Examples 152 to 154 Evaluation of Weather Resistance of Painted Film-1

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a float plate glasswas prepared as the substrate. The preheated glass substrate wasspray-coated with the mixture of the intermediate layer coating liquiddescribed in M-2 of Table 14 and a colored pigment and dried at 120° C.to obtain the intermediate layer. The solid concentration of the resinin the M-2 solution was about 20%. The film thickness of theintermediate layer measured by scanning electron microscopic observationwas about 10 μm for any of Examples 152 to 154.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, and water as thesolvent were mixed in the compounding ratio shown in T-1, T-4 and T-5 ofTable 15 to obtain the photocatalytic coating liquid. The total solidconcentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass. The preheatedintermediate layer coated body was spray-coated with the photocatalyticcoating liquid and was dried at 120° C. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 152 to 154. In thisway, the intermediate layer and the photocatalytic layer were formed toobtain the photocatalyst-coated body.

The weather resistance test for the photocatalyst-coated body of thesize of 50×100 mm thus obtained was performed as follows. Thephotocatalyst-coated body was put into a sunshine weatherometer (S-300Cmanufactured by Suga Test Instruments Co., Ltd.) defined in JIS B7753.The sample was taken out after 300 hours and the color difference beforeand after the acceleration test was measured using a color differencemeter ZE2000 manufactured by Nippon Denshoku Industries Co., Ltd. Thedegree of discoloration was evaluated by comparing the Δb values.

The results obtained are shown in Table 23. “G” in the table representslittle discoloration and “NG” represents that the Δb value transited toplus side (yellowing side). As shown in Table 23, it was found that thephotocatalyst-coated bodies of Examples 152 and 153 have sufficientweather resistance even if the intermediate layer comprising a smallamount of silicon atom is painted with the photocatalytic layer.

TABLE 23 Photocatalyst content in Intermediate Photocatalyticphotocatalytic layer layer layer (parts by mass) Δb Example 152 M-2 T-14.5 G Example 153 M-2 T-5 2 G Example 154 M-2 T-4 30 NG

Example 155 and 156 Evaluation of Weather Resistance of Painted Film-2

The photocatalyst-coated body comprising the intermediate layer and thephotocatalytic layer was produced as follows. First, a zinc-plated steelsheet painted with a general-purpose epoxy resin primer and dried wasprepared as the substrate. The substrate was spray-coated with theintermediate layer coating liquid described in M-1 and M-3 of Table 14and dried at 120° C. to obtain the intermediate layer. The solidconcentration of the resin in the M-1 and M-2 solutions was about 20%.The film thickness of the intermediate layer measured by scanningelectron microscopic observation was about 10 μm for any of Examples 155using M-1 and Example 156 using M-3.

Meanwhile, the titania water dispersion as the photocatalyst, the waterdispersed colloidal silica as the inorganic oxide, water as the solvent,and the surfactant were mixed in the compounding ratio shown in T-1 ofTable 15 to obtain the photocatalytic coating liquid. The photocatalyticcoating liquid does not comprise the hydrolyzable silicone. The totalsolid concentration of the photocatalyst and the inorganic oxide in thephotocatalytic coating liquid was 5.5% by mass. The preheatedintermediate layer coated body was spray-coated with the photocatalyticcoating liquid and was dried at 120° C. The film thickness of thephotocatalytic layer measured by scanning electron microscopicobservation was about 0.5 μm for any of Examples 55 and 56. In this way,the intermediate layer and the photocatalytic layer were formed toobtain the photocatalyst-coated body.

The weather resistance test for the photocatalyst-coated body of thesize of 50×100 mm thus obtained was performed as follows. Thephotocatalyst-coated body was put into a metaling weatherometer (M6Tmanufactured by Suga Test Instruments Co., Ltd.) and the externalappearance was confirmed after 150 hours.

In Example 155 in which the acrylic modified silicone resin comprising10% by mass of silicon atom was used, cracks did not occur and goodweather resistance was attained. On the other hand, in Example 156 inwhich the acrylic modified silicone resin comprising 16.5% by mass ofsilicon atom was used, partial occurrence of cracks was observed albeitonly slightly.

1. A photocatalyst-coated body comprising a substrate and a photocatalyst layer provided on the substrate, the photocatalyst layer comprising: photocatalyst particles of 1 part or more by mass and less than 20 parts by mass; inorganic oxide particles of 70 parts or more by mass and less than 99 parts by mass; and the dried substance of a hydrolyzable silicone of zero parts or more by mass and less than 10 parts by mass, provided that a total amount of the photocatalyst particles, the dried substance of the inorganic oxide particles and the hydrolyzable silicone is 100 parts by mass in terms of silica, wherein the photocatalyst layer has a film thickness of 3.0 μm or less.
 2. The photocatalyst-coated body according to claim 1, wherein the photocatalyst layer has a film thickness ranging from 0.5 .μm to 3.0 .μm.
 3. The photocatalyst-coated body according to claim 1, wherein the photocatalyst layer is substantially free from the hydrolyzable silicone.
 4. The photocatalyst-coated body according to claim 1, wherein the photocatalyst layer further comprises a surfactant of zero parts or more by mass and less than 10 parts by mass.
 5. The photocatalyst-coated body according to claim 1, wherein the photocatalyst layer comprises the photocatalyst particles of 1 parts to 15 parts by mass.
 6. The photocatalyst-coated body according to claim 1, wherein the photocatalyst layer comprises the photocatalyst particles of 5 parts to 15 parts by mass.
 7. The photocatalyst-coated body according to claim 1, wherein the photocatalyst particles are titanium oxide particles.
 8. The photocatalyst-coated body according to claim 1, wherein the inorganic oxide particles are silica particles.
 9. The photocatalyst-coated body according to claim 1, wherein the inorganic oxide has a number average particle diameter ranging from 10 nm or more to less than 40 nm calculated by measuring lengths of 100 particles randomly selected from particles located within a visible field magnified 200,000 times by a scanning electron microscope.
 10. The photocatalyst-coated body according to claim 1, wherein the substrate has at least a surface comprising an organic material.
 11. The photocatalyst-coated body according to claim 10, wherein the photocatalyst layer is applied directly on the substrate.
 12. The photocatalyst-coated body according to claim 1, wherein the photocatalyst-coated body is used as an exterior material.
 13. A photocatalyst coating liquid used for manufacturing the photocatalyst-coated body according to claim 1, comprising, in a solvent, photocatalyst particles of 1 part or more by mass and less than 20 parts by mass; inorganic oxide particles of 70 parts or more by mass and less than 99 parts by mass; and a hydrolyzable silicone of zero parts or more by mass and less than 10 parts by mass, provided that the total amount of the photocatalyst particles, the inorganic oxide particles and the hydrolyzable silicone is 100 parts by mass.
 14. The photocatalyst coating liquid according to claim 13, being substantially free from the hydrolyzable silicone.
 15. The photocatalyst coating liquid according to claim 13, further comprising a surfactant of zero parts or more by mass and less than 10 parts by mass.
 16. The photocatalyst coating liquid according to claim 13, comprises the photocatalyst particles of 5 parts to 15 parts by mass.
 17. The photocatalyst coating liquid according to claim 13, wherein the photocatalyst particles are titanium oxide particles.
 18. The photocatalyst coating liquid according to claim 13, wherein the inorganic oxide particles are silica particles.
 19. The photocatalyst coating liquid according to claim 13, wherein the inorganic oxide has a number average particle diameter ranging from 10 nm or more to less than 40 nm calculated by measuring lengths of 100 particles randomly selected from particles located within a visible field magnified 200,000 times by a scanning electron microscope.
 20. The photocatalyst coating liquid according to claim 13, wherein the photocatalyst coating liquid is used for applying a coating to a substrate having at least a surface comprising an organic material.
 21. The photocatalyst coating liquid according to claim 20, wherein the photocatalyst coating liquid is applied directly on the substrate.
 22. The photocatalyst coating liquid according to claim 13, wherein the photocatalyst coating liquid is used for coating an exterior material. 